Client Server Desync on observed/real container inventories

Affects 1.2.11.

This bug is stopping me from creating custom "recipes" or puzzle locks for some Marketplace projects. Basically if the inventory of a container like a dropper is changed by the server while the client is looking inside, the client does not observer the change, allowing for item duplication and general confusion on the part of the player.

Steps to reproduce.

• Place down a dropper face up containing an item of choice. (Your recipe result)
• Place down a second dropper face up containing some other items (your recipe)
• While a player is looking inside the second dropper, clone the first dropper to the second using replace. This can be done using a second player or a timer.

The player looking inside the second dropper will still see the contents unchanged however the server will consider the contents to contain the same as the first dropper. A second player looking in the dropper will at this point see a copy of the first dropper even though the first player still sees the original second dropper contents.

Despite the server thinking the dropper contains new items, the player is still able to remove the items that used to be there even though the server doesn't think they exist.

If the player exits the dropper inventory and looks inside again, they will see the contents of the first dropper, correctly synched with the server again but with some items that didn't exist safely stored in their inventory.

EDIT: Greggo asked me to clarify what I mean by client/server. This may be a Java edition term where even in Singleplayer, the game is actually running a server on the client's machine. The above bug can happen in singleplayer and is not something I have observed on a specific server or multiplayer world.