When the player holds down their 'Swap Hands' key on an item and rotates their cursor around different slots while doing so, items will be duplicated in the inventory. These items are not ghost items, as when the player picks then up with their cursor they do not disappear. This issue is specific to a multiplayer server, and cannot be reproduced in singleplayer, or an LAN world.

Steps to Reproduce:

1. Join a multiplayer server
2. Put one or more items inside your inventory
3. Press and continue holding down the 'Swap Hands' key while hovering over the item
4. Move the cursor quickly over different slots

Observed Behavior:

The item(s) will be duplicated as real items, meaning they are not "ghost items".

Expected Behavior:

The items would not be duplicated, and would properly switch as in singleplayer.

Screenshots/Videos:

1. Singleplayer:
   SinglePlayer.mp4

1. Multiplayer:
   1. Item deletion:
      MultiplayerItemDelete.mp4
   2. Item duplication:
      MultiplayerItemDuplicate.mp4

Notes:

1. This was discovered while testing MC-190503
2. (1.20.4 is not added as an affected version because of a lack of resources to test on a multiplayer server, not because I was unable to reproduce it in said version)