The mod: https://forum.mechaenetia.com/t/prospectors-journal/1327
The issue:
It looks like MultiTileEntityRock.class and etc are relocated from "gregtech/tileentity/placeables/" of original mod
to "gregtech/tileentity/misc/" folder of GT6u, that causes crash when trying to pick up the rock
crash-2024-12-13_10.02.25-server.txt