If you right click an item stack in your backpack to add on to that stack, the item stack on your cursor will get decremented, but the stack in your backpack will remain the same size.

Also affects using scroll wheel to add items to your backpack. I have MouseTweaks installed on this mod pack, so that might have something to do with it, if it can't be replicated.

Quark version: r1.5-156
MouseTweaks version: 2.10-mc1.12.2

u g h

i hate these backpack issues. so much minute detail to pick apart.

Still seem to be having issues with this in r1.5-159. Now when right clicking to add to a stack in the backpack, it adds to the stack in hand instead. As well, when left or right clicking an item that's already in the backpack, the item gets deleted. Shift + left/right works at least.