When shift clicking stacks of items from inventory(y button) into containers or villager ui, while there is one slot on your hotbar with for example 8 of the same items. You shift the most of the stack to your hotbar and only 8 into the container.

Edit by DrAwesome4333
Steps to Reproduce:
Have over a stack of cobble stone split into 2 inventory slots.
1 slot should be in inventory, the other should be a partial one on the hot bar
Open a container.
Shift click the stack in the inventory (or press Y for console)
Notice how the stack will split by first filling the stack on the hot bar and then moving the rest into the container

Expected results:
All of the selected stack should move to the container.