Version: 2.5.0 What is the bug: If you split a stack then try to add another stack to the split, it's not even the second time. e.g. if I have two stacks of cobble and I go to compress them by dragging the first stack through the crafting table slots, then drag the second stack through the same slots, the first slot will have a bunch of cobble the others won't have as much. Mod & Version: Paste.feed-the-beast.com log: Can it be repeated: Yes, consistently. Known Fix: Disable mouse tweaks. This was my quick solution, you can likely disable one config to fix this issue.