Here's the log:

Time: 10/18/21 10:48 PM
Description: Exception in server tick loop

java.lang.NoClassDefFoundError: gregtech.tileentity.misc.MultiTileEntityRock
at com.github.canisartorus.prospectorjournal.JournalBehaviour.lookForSample(JournalBehaviour.java:60)
at com.github.canisartorus.prospectorjournal.RightClickEvent.playerRightClick(RightClickEvent.java:30)
at cpw.mods.fml.common.eventhandler.ASMEventHandler_495_RightClickEvent_playerRightClick_PlayerInteractEvent.invoke(.dynamic)
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:54)
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:140)
at net.minecraftforge.event.ForgeEventFactory.onPlayerInteract(ForgeEventFactory.java:100)
at net.minecraft.server.management.ItemInWorldManager.func_73078_a(ItemInWorldManager.java:353)
at net.minecraft.network.NetHandlerPlayServer.func_147346_a(NetHandlerPlayServer.java:556)
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:60)
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:9)
at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212)
at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:186)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:396)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)
Caused by: java.lang.ClassNotFoundException: gregtech.tileentity.misc.MultiTileEntityRock
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClassHelper(ClassLoader.java:953)
at java.lang.ClassLoader.loadClass(ClassLoader.java:898)
at java.lang.ClassLoader.loadClass(ClassLoader.java:881)
... 17 more
Caused by: java.lang.NullPointerException
at org.objectweb.asm.ClassReader.(Unknown Source)
at sereneseasons.asm.transformer.WeatherTransformer.transform(WeatherTransformer.java:21)
at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176)
... 20 more

Thanks in advance for any help with this issue!

Which version of Gregtech are you using?

I've just discovered the 6.14.21 pre-release secret versions have changed package structure for that class, and will not be compatible.

Oh yeah, that would explain it, I'm using one of the latest secret versions.
Thanks for the quick reply!

Hate to be a bother again, the game doesn't seem to be able to find the latest public release of gregtech 6 (6.14.21) when it is installed, even if it's set as a dependency.

[.. , ..) is "set notation", prior fix was to reject versions of Gregtech 6.14.21 and higher.
The version PJ 0.12 that is compatible with just-released GT will be along today.

Yeah sorry to just keep re-opening, but it's still doing the thing.

.