When setting a spawn point using a non-fully charged Respawn Anchor while holding a block other than Glowstone in the main hand, the block disappears after it is placed. When doing the same but holding it in the offhand, the spawn point is set and the block is placed normally.
Logging out from the world and then back, going through a portal, or obtaining the same block that was placed will revert the player back to normal.
- Enter the Nether, place a Respawn Anchor, and then charge it with Glowstone but not until maximum charge.
- Hold another block other than Glowstone in the main hand, and then set your spawn point using the Respawn Anchor.
→ The block disappears after it is placed.