[1.10.2] Extrautils2 crashes ONLY in workspace.

[LaureeGrd]

Hi, sorry if the title is not very descriptive. I don't know how to describe what's happening to me.
Today I wanted to continue with my very basic mod, the Pen Pineapple Apple Pen mod. This is just a project to learn how to make better mods actually.
The thing is, it has an incompatibility problem with Extra Utilities 2. So I wanted to fix that and in order to replicate the issue, I dropped the Extrautils jar inside the mods folder of my workspace, but it crashes with the following error:

 

Spoiler

---- Minecraft Crash Report ----
// Would you like a cupcake?

Time: 05/07/17 00:06
Description: There was a severe problem during mod loading that has caused the game to fail

net.minecraftforge.fml.common.LoaderExceptionModCrash: Caught exception from Extra Utilities 2 (extrautils2)
Caused by: java.lang.RuntimeException: com.rwtema.extrautils2.gui.backend.DynamicContainer$PacketGUIInput can't be created
	at com.rwtema.extrautils2.network.NetworkHandler.registerPacket(NetworkHandler.java:109)
	at com.rwtema.extrautils2.network.NetworkHandler.init(NetworkHandler.java:33)
	at com.rwtema.extrautils2.ExtraUtils2.preInit(ExtraUtils2.java:122)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:618)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
	at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
	at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
	at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
	at com.google.common.eventbus.EventBus.post(EventBus.java:275)
	at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:243)
	at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:221)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
	at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
	at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
	at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
	at com.google.common.eventbus.EventBus.post(EventBus.java:275)
	at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:145)
	at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:624)
	at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:259)
	at net.minecraft.client.Minecraft.startGame(Minecraft.java:477)
	at net.minecraft.client.Minecraft.run(Minecraft.java:386)
	at net.minecraft.client.main.Main.main(Main.java:118)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at net.minecraftforge.gradle.GradleStartCommon.launch(GradleStartCommon.java:97)
	at GradleStart.main(GradleStart.java:26)
Caused by: java.lang.NoClassDefFoundError: com/rwtema/extrautils2/gui/backend/DynamicContainer
	at java.lang.Class.getDeclaringClass0(Native Method)
	at java.lang.Class.getDeclaringClass(Unknown Source)
	at java.lang.Class.getEnclosingClass(Unknown Source)
	at java.lang.Class.getSimpleBinaryName(Unknown Source)
	at java.lang.Class.getSimpleName(Unknown Source)
	at com.rwtema.extrautils2.network.PacketCodec.addClass(PacketCodec.java:37)
	at com.rwtema.extrautils2.network.NetworkHandler.registerPacket(NetworkHandler.java:103)
	... 45 more
Caused by: java.lang.ClassNotFoundException: com.rwtema.extrautils2.gui.backend.DynamicContainer
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	... 52 more
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: com.rwtema.extrautils2.gui.backend.WidgetTextTranslate
	at org.objectweb.asm.ClassWriter.getCommonSuperClass(ClassWriter.java:1684)
	at org.objectweb.asm.ClassWriter.getMergedType(ClassWriter.java:1654)
	at org.objectweb.asm.Frame.merge(Frame.java:1426)
	at org.objectweb.asm.Frame.merge(Frame.java:1325)
	at org.objectweb.asm.MethodWriter.visitMaxs(MethodWriter.java:1475)
	at org.objectweb.asm.commons.LocalVariablesSorter.visitMaxs(LocalVariablesSorter.java:170)
	at org.objectweb.asm.ClassReader.readCode(ClassReader.java:1554)
	at org.objectweb.asm.ClassReader.readMethod(ClassReader.java:1017)
	at org.objectweb.asm.ClassReader.accept(ClassReader.java:693)
	at org.objectweb.asm.ClassReader.accept(ClassReader.java:506)
	at net.minecraftforge.fml.common.asm.transformers.DeobfuscationTransformer.transform(DeobfuscationTransformer.java:51)
	at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279)
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176)
	... 54 more


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

-- System Details --
Details:
	Minecraft Version: 1.10.2
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.8.0_72, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 353561608 bytes (337 MB) / 729284608 bytes (695 MB) up to 1901592576 bytes (1813 MB)
	JVM Flags: 0 total; 
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	FML: MCP 9.32 Powered by Forge 12.18.3.2316 5 mods loaded, 5 mods active
	States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
	UCH	mcp{9.19} [Minecraft Coder Pack] (minecraft.jar) 
	UCH	FML{8.0.99.99} [Forge Mod Loader] (forgeSrc-1.10.2-12.18.3.2316.jar) 
	UCH	Forge{12.18.3.2316} [Minecraft Forge] (forgeSrc-1.10.2-12.18.3.2316.jar) 
	UCH	ppapmod{1.5.1} [PPAP Mod] (bin) 
	UCE	extrautils2{1.0} [Extra Utilities 2] (extrautils2-1.10.2-1.4.4.jar) 
	Loaded coremods (and transformers): 
	GL info: ' Vendor: 'ATI Technologies Inc.' Version: '4.5.13417 Compatibility Profile Context 15.301.1901.0' Renderer: 'AMD Radeon HD 6570'

 

I really don't know why it wouldn't be able to create that class (and this same .jar works outside of the development environment).
Project is running Java 8 (update 72 if that's a problem). I could update it if needed.

Thanks.