This code keeps popping up after I put "Oh the biomes you'll go" into my mods folder, it was working before this as it's my first mod I added into my folder so I'm a bit confused on if it's a problem with the mod or forge itself.

Error: org.spongepowered.asm.mixin.transformer.throwables.MixinTransformerError: An unexpected critical error was encountered

---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.

Time: 3/20/22, 12:28 PM
Description: Initializing game

org.spongepowered.asm.mixin.transformer.throwables.MixinTransformerError: An unexpected critical error was encountered
    at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:392) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:250) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.service.modlauncher.MixinTransformationHandler.processClass(MixinTransformationHandler.java:131) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.launch.MixinLaunchPluginLegacy.processClass(MixinLaunchPluginLegacy.java:131) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at cpw.mods.modlauncher.serviceapi.ILaunchPluginService.processClassWithFlags(ILaunchPluginService.java:156) ~[modlauncher-9.1.3.jar:9.1.3+9.1.3+main.9b69c82a] {}
    at cpw.mods.modlauncher.LaunchPluginHandler.offerClassNodeToPlugins(LaunchPluginHandler.java:88) ~[modlauncher-9.1.3.jar:?] {}
    at cpw.mods.modlauncher.ClassTransformer.transform(ClassTransformer.java:120) ~[modlauncher-9.1.3.jar:?] {}
    at cpw.mods.modlauncher.TransformingClassLoader.maybeTransformClassBytes(TransformingClassLoader.java:50) ~[modlauncher-9.1.3.jar:?] {}
    at cpw.mods.cl.ModuleClassLoader.readerToClass(ModuleClassLoader.java:110) ~[securejarhandler-1.0.3.jar:?] {}
    at cpw.mods.cl.ModuleClassLoader.lambda$findClass$16(ModuleClassLoader.java:216) ~[securejarhandler-1.0.3.jar:?] {}
    at cpw.mods.cl.ModuleClassLoader.loadFromModule(ModuleClassLoader.java:226) ~[securejarhandler-1.0.3.jar:?] {}
    at cpw.mods.cl.ModuleClassLoader.findClass(ModuleClassLoader.java:216) ~[securejarhandler-1.0.3.jar:?] {}
    at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:132) ~[securejarhandler-1.0.3.jar:?] {}
    at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
    at net.minecraft.client.Minecraft.<init>(Minecraft.java:516) ~[client-1.18.2-20220228.144236-srg.jar%2353!/:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
    at net.minecraft.client.main.Main.main(Main.java:169) ~[client-1.18.2-20220228.144236-srg.jar%2353!/:?] {re:classloading,pl:runtimedistcleaner:A}
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] {}
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?] {}
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] {}
    at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?] {}
    at net.minecraftforge.fml.loading.targets.CommonClientLaunchHandler.lambda$launchService$0(CommonClientLaunchHandler.java:45) ~[fmlloader-1.18.2-40.0.19.jar%2316!/:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-9.1.3.jar%235!/:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:53) [modlauncher-9.1.3.jar%235!/:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:71) [modlauncher-9.1.3.jar%235!/:?] {}
    at cpw.mods.modlauncher.Launcher.run(Launcher.java:106) [modlauncher-9.1.3.jar%235!/:?] {}
    at cpw.mods.modlauncher.Launcher.main(Launcher.java:77) [modlauncher-9.1.3.jar%235!/:?] {}
    at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26) [modlauncher-9.1.3.jar%235!/:?] {}
    at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23) [modlauncher-9.1.3.jar%235!/:?] {}
    at cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:149) [bootstraplauncher-1.0.0.jar:?] {}
Caused by: org.spongepowered.asm.mixin.throwables.MixinApplyError: Mixin [byg.mixins.json:server.MixinMinecraftServer] from phase [DEFAULT] in config [byg.mixins.json] FAILED during APPLY
    at org.spongepowered.asm.mixin.transformer.MixinProcessor.handleMixinError(MixinProcessor.java:636) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.MixinProcessor.handleMixinApplyError(MixinProcessor.java:588) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:379) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    ... 28 more
Caused by: org.spongepowered.asm.mixin.transformer.throwables.InvalidMixinException: @Shadow field field_240767_f_ was not located in the target class net.minecraft.server.MinecraftServer. Using refmap byg.refmap.json
    at org.spongepowered.asm.mixin.transformer.MixinPreProcessorStandard.attachFields(MixinPreProcessorStandard.java:629) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.MixinPreProcessorStandard.attach(MixinPreProcessorStandard.java:305) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.MixinPreProcessorStandard.createContextFor(MixinPreProcessorStandard.java:280) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.MixinInfo.createContextFor(MixinInfo.java:1288) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.MixinApplicatorStandard.apply(MixinApplicatorStandard.java:292) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.TargetClassContext.apply(TargetClassContext.java:383) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.TargetClassContext.applyMixins(TargetClassContext.java:365) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:363) ~[mixin-0.8.5.jar:0.8.5+Jenkins-b310.git-155314e6e91465dad727e621a569906a410cd6f4] {}
    ... 28 more
 

Problem with Oh The Biomes You'll Go. Make sure you are using the latest version.
If the Mod is already up to date, report this bug to the Mod author.