Using /item to replace the item in a player's hotbar slot frequently creates ghost items. Right-clicking with a ghost item will still place a block, but it does not show up in the hotbar.
This did not happen in 1.16.5.
- Set up a repeating command block with the following command:
- Drop the dirt block
→ The slot will become empty, even though the /item command should refill it
- Press Q again while selecting the first slot
→ You'll drop dirt, even though there's no dirt in that slot
- Right-click onto a block while selecting the first slot
→ A dirt block gets placed
- Quick demonstration: Minecraft 1.17 Release Candidate 1 - Singleplayer 2021-06-05 14-59-59_Trim.mp4
- Slime blocks turning into a ghost item for the first time (1:50)
- This clip showcases buggy offhand behaviour (1:09)
- A brief encounter with ghost items (0:19)
- This clip contains some interesting events that may have caused the ghost items (1:15)
- This video shows that death fixes the ghost item (0:18) (~3mins cut out)