Inventory: Single Stack Items don't drop off into a slot when cursor is moving

Go into minecraft (creative, survival also affected but just for ease)
grab an item (single item) and swing your cursor left and right while trying to drop an item off into a slot in your inventory
in 16w44a the item does not get dropped from the mouse.
in 16w43a it did drop into the correct slot from the mouse.

For clarification:
https://www.youtube.com/watch?v=Y1-4h02eFv4
This shows the new and old behaviour