Dragging a stack to split it in the inventory/crafting window using left or right click will stick when either mouse button is released and the stack will continue to split when trying to put remaining items back in inventory.
Other times, clicking to begin the split will not register properly.
Both happen more often than not and were done with a wired mouse having no known issues with other applications.
Does this bug still appear in 0.13.1? If so please respond.