Minecraft Japan Forum

長くなってしまってすみません、使っていた環境にmetamorphを導入しました。他のmodのみの時はクラッシュしなかったのでmetamorphが原因だと思われます。
Metamorphで変身しようとするとクラッシュしてしまいました。それ以外は影響がなかった（導入してから10分ほどプレイ）
のですが、解決策などありますでしょうか？

---- Minecraft Crash Report ----

WARNING: coremods are present:
EnderCorePlugin (EnderCore-1.12.2-0.5.76-core.jar)
McLib core mod (mclib-2.2.1-1.12.2.jar)
ForgelinPlugin (Forgelin-1.8.4.jar)
MekanismCoremod (Mekanism-1.12.2-9.8.3.390.jar)
OpenModsCorePlugin (OpenModsLib-1.12.2-0.12.2.jar)
CTMCorePlugin (CTM-MC1.12.2-1.0.2.31.jar)
Contact their authors BEFORE contacting forge

// My bad.

Time: 2/9/21 8:50 PM
Description: Unexpected error

java.lang.NoClassDefFoundError: mchorse/mclib/client/gui/framework/elements/GuiButtonElement
at mchorse.metamorph.client.gui.GuiSurvivalMenu.<init>(GuiSurvivalMenu.java:41)
at mchorse.metamorph.client.KeyboardHandler.onKey(KeyboardHandler.java:115)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_1461_KeyboardHandler_onKey_KeyInputEvent.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
at net.minecraftforge.fml.common.FMLCommonHandler.fireKeyInput(FMLCommonHandler.java:565)
at net.minecraft.client.Minecraft.func_184118_az(Minecraft.java:2017)
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1808)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1098)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:398)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.ClassNotFoundException: mchorse.mclib.client.gui.framework.elements.GuiButtonElement
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 17 more
Caused by: java.lang.NullPointerException


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Client thread
Stacktrace:
at mchorse.metamorph.client.gui.GuiSurvivalMenu.<init>(GuiSurvivalMenu.java:41)
at mchorse.metamorph.client.KeyboardHandler.onKey(KeyboardHandler.java:115)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_1461_KeyboardHandler_onKey_KeyInputEvent.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
at net.minecraftforge.fml.common.FMLCommonHandler.fireKeyInput(FMLCommonHandler.java:565)
at net.minecraft.client.Minecraft.func_184118_az(Minecraft.java:2017)

-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [EntityPlayerSP['WatanabeEnju'/584, l='MpServer', x=-137.80, y=4.00, z=-875.00]]
Chunk stats: MultiplayerChunkCache: 552, 552
Level seed: 0
Level generator: ID 01 - flat, ver 0. Features enabled: false
Level generator options:
Level spawn location: World: (-144,4,-887), Chunk: (at 0,0,9 in -9,-56; contains blocks -144,0,-896 to -129,255,-881), Region: (-1,-2; contains chunks -32,-64 to -1,-33, blocks -512,0,-1024 to -1,255,-513)
Level time: 992 game time, 1993 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
Forced entities: 32 total; [EntitySheep['ヒツジ'/662, l='MpServer', x=-66.50, y=4.00, z=-815.50], EntityPlayerSP['WatanabeEnju'/584, l='MpServer', x=-137.80, y=4.00, z=-875.00], EntitySheep['ヒツジ'/667, l='MpServer', x=-73.19, y=4.00, z=-821.31], EntitySheep['ヒツジ'/671, l='MpServer', x=-61.50, y=4.00, z=-812.50], EntitySheep['ヒツジ'/674, l='MpServer', x=-77.25, y=4.00, z=-809.60], EntityDonkey['ロバ'/678, l='MpServer', x=-141.54, y=4.00, z=-911.74], EntityDonkey['ロバ'/679, l='MpServer', x=-141.46, y=4.00, z=-912.93], EntityPig['ブタ'/680, l='MpServer', x=-137.50, y=4.00, z=-917.50], EntityPig['ブタ'/681, l='MpServer', x=-136.50, y=4.00, z=-919.50], EntityCow['ウシ'/682, l='MpServer', x=-154.50, y=4.00, z=-812.50], EntityCow['ウシ'/683, l='MpServer', x=-149.50, y=4.00, z=-814.50], EntityCow['ウシ'/684, l='MpServer', x=-151.50, y=4.00, z=-809.50], EntityCow['ウシ'/685, l='MpServer', x=-157.13, y=4.00, z=-806.87], EntitySheep['ヒツジ'/623, l='MpServer', x=-187.50, y=4.00, z=-944.50], EntityPig['ブタ'/624, l='MpServer', x=-194.50, y=4.00, z=-945.50], EntitySheep['ヒツジ'/625, l='MpServer', x=-189.50, y=4.00, z=-948.50], EntitySheep['ヒツジ'/626, l='MpServer', x=-190.50, y=4.00, z=-947.50], EntitySheep['ヒツジ'/627, l='MpServer', x=-71.50, y=4.00, z=-839.50], EntitySheep['ヒツジ'/628, l='MpServer', x=-73.50, y=4.00, z=-837.50], EntitySheep['ヒツジ'/629, l='MpServer', x=-63.76, y=4.00, z=-833.65], EntitySheep['ヒツジ'/630, l='MpServer', x=-70.50, y=4.00, z=-841.50], EntityCow['ウシ'/631, l='MpServer', x=-86.50, y=4.00, z=-847.50], EntityCow['ウシ'/632, l='MpServer', x=-87.50, y=4.00, z=-848.50], EntityHorse['ウマ'/633, l='MpServer', x=-91.50, y=4.00, z=-851.50], EntitySheep['ヒツジ'/634, l='MpServer', x=-92.50, y=4.00, z=-809.50], EntityDonkey['ロバ'/698, l='MpServer', x=-173.04, y=4.00, z=-946.47], EntitySheep['ヒツジ'/635, l='MpServer', x=-91.50, y=4.00, z=-813.50], EntityDonkey['ロバ'/699, l='MpServer', x=-171.65, y=4.00, z=-947.26], EntitySheep['ヒツジ'/636, l='MpServer', x=-94.50, y=4.00, z=-813.50], EntityDonkey['ロバ'/700, l='MpServer', x=-172.31, y=4.00, z=-946.08], EntitySheep['ヒツジ'/637, l='MpServer', x=-94.50, y=4.00, z=-814.50], EntityChicken['ニワトリ'/701, l='MpServer', x=-178.50, y=4.00, z=-940.50]]
Retry entities: 0 total; []
Server brand: fml,forge
Server type: Integrated singleplayer server
Stacktrace:
at net.minecraft.client.multiplayer.WorldClient.func_72914_a(WorldClient.java:532)
at net.minecraft.client.Minecraft.func_71396_d(Minecraft.java:2741)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:427)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.12.2
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 3727780936 bytes (3555 MB) / 7583301632 bytes (7232 MB) up to 8589934592 bytes (8192 MB)
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx8G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP 9.42 Powered by Forge 14.23.5.2854 Optifine OptiFine_1.12.2_HD_U_F5 86 mods loaded, 85 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored

| State | ID | Version | Source | Signature |
|:------ |:----------------------------------------- |:----------------- |:---------------------------------------------- |:---------------------------------------- |
| LCHIJA | minecraft | 1.12.2 | minecraft.jar | None |
| LCHIJA | mcp | 9.42 | minecraft.jar | None |
| LCHIJA | FML | 8.0.99.99 | forge-1.12.2-14.23.5.2854.jar | e3c3d50c7c986df74c645c0ac54639741c90a557 |
| LCHIJA | forge | 14.23.5.2854 | forge-1.12.2-14.23.5.2854.jar | e3c3d50c7c986df74c645c0ac54639741c90a557 |
| LCHIJA | openmodscore | 0.12.2 | minecraft.jar | None |
| LCHIJA | mobconfinement | 1.12.2-1.0 | [1.12.2]MobConfinement-1.0.jar | None |
| LCHIJA | net.minecraft.scalar.cutall.mod_cutallsmp | 2.5.2 | [1.12][forge2413]mod_CutAllSMP_v2.5.2.jar | None |
| LCHIJA | jei | 4.15.0.296 | jei_1.12.2-4.15.0.296.jar | None |
| LCHIJA | appleskin | 1.0.14 | AppleSkin-mc1.12-1.0.14.jar | None |
| LCHIJA | ctm | MC1.12.2-1.0.2.31 | CTM-MC1.12.2-1.0.2.31.jar | None |
| LCHIJA | appliedenergistics2 | rv6-stable-7 | appliedenergistics2-rv6-stable-7.jar | dfa4d3ac143316c6f32aa1a1beda1e34d42132e5 |
| LCHIJA | baubles | 1.5.2 | Baubles-1.12-1.5.2.jar | None |
| LCHIJA | cyclicmagic | 1.20.8 | Cyclic-1.12.2-1.20.8.jar | 0e5cb559be7d03f3fc18b8cba547d663e25f28af |
| LCHIJA | guideapi | 1.12-2.1.8-63 | Guide-API-1.12-2.1.8-63.jar | None |
| LCHIJA | bloodmagic | 1.12.2-2.4.3-105 | BloodMagic-1.12.2-2.4.3-105.jar | None |
| LCHIJA | botania | r1.10-363 | Botania+r1.10-363.jar | None |
| LCHIJA | codechickenlib | 3.2.3.358 | CodeChickenLib-1.12.2-3.2.3.358-universal.jar | f1850c39b2516232a2108a7bd84d1cb5df93b261 |
| LCHIJA | chickenchunks | 2.4.2.74 | ChickenChunks-1.12.2-2.4.2.74-universal.jar | f1850c39b2516232a2108a7bd84d1cb5df93b261 |
| LCHIJA | redstoneflux | 2.1.1 | RedstoneFlux-1.12-2.1.1.1-universal.jar | None |
| LCHIJA | cofhcore | 4.6.6 | CoFHCore-1.12.2-4.6.6.1-universal.jar | None |
| LCHIJA | cofhworld | 1.4.0 | CoFHWorld-1.12.2-1.4.0.1-universal.jar | None |
| LCHIJA | endercore | 1.12.2-0.5.76 | EnderCore-1.12.2-0.5.76.jar | None |
| LCHIJA | thermalfoundation | 2.6.7 | ThermalFoundation-1.12.2-2.6.7.1-universal.jar | None |
| LCHIJA | enderio | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderiointegrationtic | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderiobase | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderioconduits | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderioconduitsappliedenergistics | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderioconduitsopencomputers | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderioconduitsrefinedstorage | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderiointegrationforestry | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderiointegrationticlate | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderioinvpanel | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderiomachines | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | enderiopowertools | 5.2.65 | EnderIO-1.12.2-5.2.65.jar | None |
| LCHIJA | energyconverters | 1.3.7.30 | energyconverters_1.12.2-1.3.7.30.jar | None |
| LCHIJA | waila | 1.8.26 | Hwyla-1.8.26-B41_1.12.2.jar | None |
| LCHIJA | extracells | 2.6.5 | ExtraCells-1.12.2-2.6.5.jar | None |
| LCHIJA | extrautils2 | 1.0 | extrautils2-1.12-1.9.9.jar | None |
| LCHIJA | forgelin | 1.8.4 | Forgelin-1.8.4.jar | None |
| LCHIJA | gvclib | 1.12.2 | GVCLib__1.12.2__3.1.zip | None |
| LCHIJA | hmggirlfront | 1.12.2 | HMGDollsFrontLine1.12.2.β.17.0.zip | None |
| LCHIJA | ic2 | 2.8.170-ex112 | industrialcraft-2-2.8.170-ex112.jar | de041f9f6187debbc77034a344134053277aa3b0 |
| LCHIJA | mekanism | 1.12.2-9.8.3.390 | Mekanism-1.12.2-9.8.3.390.jar | None |
| LCHIJA | teslacorelib | 1.0.17 | tesla-core-lib-1.12.2-1.0.17.jar | d476d1b22b218a10d845928d1665d45fce301b27 |
| LCHIJA | industrialforegoing | 1.12.2-1.12.2 | industrialforegoing-1.12.2-1.12.13-237.jar | None |
| LCHIJA | journeymap | 1.12.2-5.7.1 | journeymap-1.12.2-5.7.1.jar | None |
| LCHIJA | fluidtank | 12.5.2 | LargeFluidTank-12.5.2.jar | 617a4e95f0af9de5402bb9883abe0f53a6bfa230 |
| LCHIJA | fluidtank_ae2 | 12.5.2 | LargeFluidTank-12.5.2.jar | 617a4e95f0af9de5402bb9883abe0f53a6bfa230 |
| LCHIJA | fluidtank_theoneprobe | 12.5.2 | LargeFluidTank-12.5.2.jar | 617a4e95f0af9de5402bb9883abe0f53a6bfa230 |
| LCHIJA | mantle | 1.12-1.3.3.55 | Mantle-1.12-1.3.3.55.jar | None |
| LCHIJA | mcjtylib_ng | 3.5.4 | mcjtylib-1.12-3.5.4.jar | None |
| LCHIJA | mclib | 2.2.1 | mclib-2.2.1-1.12.2.jar | None |
| LCHIJA | mekanismgenerators | 1.12.2-9.8.3.390 | MekanismGenerators-1.12.2-9.8.3.390.jar | None |
| LCHIJA | mekanismtools | 1.12.2-9.8.3.390 | MekanismTools-1.12.2-9.8.3.390.jar | None |
| LCHIJA | metamorph | 1.1.7 | metamorph-1.1.7-1.12.2.jar | None |
| LCHIJA | harvestcraft | 1.12.2zb | Pam's+HarvestCraft+1.12.2zg.jar | None |
| LCHIJA | mm_lib | 2.1.0 | MMLib-2.1.0.jar | None |
| LCHIJA | numina | 1.12.2-1.0.38 | Numina-1.12.2-1.0.38.jar | None |
| LCHIJA | powersuits | 1.12.2-1.0.46 | ModularPowersuits-1.12.2-1.0.46.jar | None |
| LCHIJA | openmods | 0.12.2 | OpenModsLib-1.12.2-0.12.2.jar | d2a9a8e8440196e26a268d1f3ddc01b2e9c572a5 |
| LCHIJA | openblocks | 1.8.1 | OpenBlocks-1.12.2-1.8.1.jar | d2a9a8e8440196e26a268d1f3ddc01b2e9c572a5 |
| LCHIJA | bonecraft | 1.12.2a | Pam's+BoneCraft+1.12.2a.jar | None |
| LCHIJA | brewcraft | 1.12.2-1.0.2 | Pam's+BrewCraft+1.12.2-1.0.2.jar | None |
| LCHIJA | desertcraft | 1.12.2a | Pam's+DesertCraft+1.12.2b.jar | None |
| LCHIJA | pigskin | 1.12.2b | Pam's+Pig+Skin+1.12.2b.jar | None |
| LCHIJA | simplystrawberries | 1.12.2-1.0.0 | Pam's+Simply+Strawberries+1.12.2+-+1.0.0.jar | None |
| LCHIJA | redbudtree | 1.12.2b | PamsRedbudTree1.12.2b.jar | None |
| LCHIJA | patchouli | 1.0-20 | Patchouli-1.0-20.jar | None |
| LCHIJA | projecte | 1.12.2-PE1.4.1 | ProjectE-1.12.2-PE1.4.1.jar | None |
| LCHIJA | quickleafdecay | 1.2.4 | QuickLeafDecay-MC1.12.1-1.2.4.jar | None |
| LCHIJA | rftools | 7.73 | rftools-1.12-7.73.jar | None |
| LCHIJA | sakura | 1.0.4.1-1.12.2 | Sakura-1.0.4.1-1.12.2.jar | None |
| LCHIJA | shincolle | 1.12.2.1.0 | ShinColle-1.12.2.1.0.jar | None |
| LCHIJA | flammpfeil.slashblade | mc1.12-r33 | SlashBlade-mc1.12-r33.jar | None |
| LCHIJA | slashblade_addon | 1.6.0 | SJAP-1.6.0.jar | None |
| LCHIJA | slashblade.exblades | mc1.12.2-r1 | Slashblade-ExBlades-mc1.12.2-r1.jar | None |
| LCHIJA | tf2 | 1.0.2 | TacticalFrame2-1.12.2-alpha1.1.jar | None |
| LCHIJA | lastsmith | 2.1.2-1.12.2 | TLS-2.1.2-1.12.2.jar | None |
| LCHIJA | tofucraft | 0.1.0.9 | TofuCraftReload-0.1.0.9.jar | None |
| LCHIJA | torohealthmod | 1.12.2-11 | torohealth-1.12.2-11.jar | None |
| LCHIJA | twilightforest | 3.11.1021 | twilightforest-1.12.2-3.11.1021-universal.jar | None |
| LCHIJA | wailaharvestability | 1.1.12 | WailaHarvestability-mc1.12-1.1.12.jar | None |
| LCHIJA | wawla | 2.6.275 | Wawla-1.12.2-2.6.275.jar | d476d1b22b218a10d845928d1665d45fce301b27 |
| LCHIJA | teslacorelib_registries | 1.0.17 | tesla-core-lib-1.12.2-1.0.17.jar | None |
| UD | mclib_core | 2.2.1 | minecraft.jar | None |

Loaded coremods (and transformers):
EnderCorePlugin (EnderCore-1.12.2-0.5.76-core.jar)
com.enderio.core.common.transform.EnderCoreTransformer
com.enderio.core.common.transform.SimpleMixinPatcher
McLib core mod (mclib-2.2.1-1.12.2.jar)
mchorse.mclib.core.McLibCMClassTransformer
ForgelinPlugin (Forgelin-1.8.4.jar)

MekanismCoremod (Mekanism-1.12.2-9.8.3.390.jar)
mekanism.coremod.KeybindingMigrationHelper
OpenModsCorePlugin (OpenModsLib-1.12.2-0.12.2.jar)
openmods.core.OpenModsClassTransformer
CTMCorePlugin (CTM-MC1.12.2-1.0.2.31.jar)
team.chisel.ctm.client.asm.CTMTransformer
GL info: ' Vendor: 'ATI Technologies Inc.' Version: '4.6.13587 Compatibility Profile Context 19.40.54 26.20.14054.0' Renderer: 'AMD Radeon(TM) Graphics'
OpenModsLib class transformers: [llama_null_fix:FINISHED],[horse_base_null_fix:FINISHED],[pre_world_render_hook:FINISHED],[player_render_hook:FINISHED],[horse_null_fix:FINISHED]
AE2 Version: stable rv6-stable-7 for Forge 14.23.5.2768
Ender IO: Found the following problem(s) with your installation (That does NOT mean that Ender IO caused the crash or was involved in it in any way. We add this information to help finding common problems, not as an invitation to post any crash you encounter to Ender IO's issue tracker. Always check the stack trace above to see which mod is most likely failing.):
* Optifine is installed. This is NOT supported.
This may (look up the meaning of 'may' in the dictionary if you're not sure what it means) have caused the error. Try reproducing the crash WITHOUT this/these mod(s) before reporting it.
Authlib is : /C:/Users/Daigo/AppData/Roaming/.minecraft/libraries/com/mojang/authlib/1.5.25/authlib-1.5.25.jar

宏明2766 さんが書きました: ↑2021年2月09日(火) 22:34 長くなってしまってすみません、使っていた環境にmetamorphを導入しました。他のmodのみの時はクラッシュしなかったのでmetamorphが原因だと思われます。
Metamorphで変身しようとするとクラッシュしてしまいました。それ以外は影響がなかった（導入してから10分ほどプレイ）
のですが、解決策などありますでしょうか？

...

起きているエラーは

宏明2766 さんが書きました: ↑2021年2月09日(火) 22:34 Time: 2/9/21 8:50 PM
Description: Unexpected error

java.lang.NoClassDefFoundError: mchorse/mclib/client/gui/framework/elements/GuiButtonElement
at mchorse.metamorph.client.gui.GuiSurvivalMenu.<init>(GuiSurvivalMenu.java:41)
省略
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 17 more
Caused by: java.lang.NullPointerException

NoClassDefFoundErrorです(ただし、根本的なエラーはNullPointerExceptionです)
NoXXXErrorやNoXXXExceptionがMinecraftのプレイ中に発生した場合はバージョン関連が怪しいです。

クラッシュレポートを見る限り、metamorphのバージョンはmetamorph-1.1.7-1.12.2.jarで、
metamorphの前提バージョンはmclib-2.2.1-1.12.2.jarのようです。

CurseForgeを見る限り、metamorph-1.1.7-1.12.2.jarのリリース日は2018年12月で、mclib-2.2.1-1.12.2.jarのリリース日は3日前となり、新しい前提MODと古いmetamorphが混在していることになります。

なので、リリース日が近い物に統一することで解決しそうな気がします。
ただし、metamorphはアップデートで大きく操作方法や画面が変わっていますので、ご注意ください。


一応forge-1.12.2-14.23.5.2768にmclib-2.2.1-1.12.2.jarとmetamorph-1.1.7-1.12.2.jarのみを入れ変身ボタン"}"を押下した直後にクラッシュしたことを確認しました。 クラッシュ後metamorphをmetamorph-1.2.6-1.12.2.jarに変更することで正常に変身機能が使えるようになったことも確認しましたので、恐らく解決すると思います。(私の環境だと命令が見当たらなかったことを意味するNoSuchMethodErrorが出たことが少し気になりますが…)

もし、解決された場合トピックの鉛筆マークをクリックしてタイトルに【解決済】を付け加え、
【解決済】クラッシュについて（Metamorphみたいな感じにしてもらえると助かります。
鉛筆マークはフォーラムにログインしている必要があります。

検証(再現)まで親切にありがとうございます。
おかげさまでしっかりmetamorph生活を送れそうです！
1.7.10のmorphmodと全然違くて慣れるのに時間がかかりそうですが使えて嬉しいです。

ありがとうございました