[Bug]: Items disappear with two players having inventory menu open at the same time

[lukemango]

Expected behavior

Probably only one person being able to put items into the armor stand inventory at a time - might also be worth cancelling the interact event to prevent people putting items in whilst the GUI is open

Observed/Actual behavior

Player A opens the inventory menu, Player B opens the inventory menu. Player A puts an item into the head slot and closes the menu, player B closes the menu and it wipes it.

Short video attached. Item visibly disappears at 0:22.

Moments-clip-from-Mar-17-2024.mp4

Steps/models to reproduce

Same as observed behaviour.

Plugin list

The vast majority are custom plugins so it's not likely related. If they are required, please let me know.

Plugin Version

1.19.2-38

Server Version

[10:34:26 INFO]: This server is running UniverseSpigot version git-UniverseSpigot-"e847242" (MC: 1.20.4) (Implementing API version 1.20.4-R0.1-SNAPSHOT) (Git: e847242 on ver/1.20.4-plus)
Universe-git-UniverseSpigot-"e847242" (MC: 1.20.4)

(A PaperMC fork)

Other

No response

[Wolfieheart]

Known Issue has been around for a long time - Fixing it would require most likely moving to paper = but marked to be fixed later

[lukemango]

Known Issue has been around for a long time - Fixing it would require most likely moving to paper = but marked to be fixed later

would it not be possible to prevent player B from opening the UI at the same time as the other player?