When I use the inventory, items tend to move around as they want to with controllable. Especially with then a keyboard and mouse.
If I move an item to a specific slot, the items tend to split the stack and move into either the chest inventory or the player inventory at random.

Not sure why this is happening, I also use inventory tweaks renewed and optifine but the issue seems to lie solely with Controllable.

1.16.5 forge 36.0.1

Thanks for the report! I've done some testing and have run into the issue you have described. I will get a fix out soon.