The InventoryCloseEvent has been fired after any inventory was closed by the player for all versions prior to 1.16. This is no longer true for the player inventory. The InventoryCloseEvent is only fired for containers and crafting inventories. As this breaks quite a few plugins and requires listening for the window-close packet to circumvent, the bug is quite major for me. I have found no indication that this is a deliberate change with my searches so far.

To reproduce:

1. Create an EventListener for InventoryCloseEvent
2. In-game try closing other inventories, such as crafting tables. You will see the close event firing.
3. Try opening and closing your player inventory. No InventoryCloseEvent will be fired.