Verification builds:
Retail 1.19.4 | Java | Windows 10 – No
Snapshot 1.20 Pre-release 1 | Java | Windows 10 – Yes
Snapshot 1.20 Pre-release 1 | Java | Windows 8.1 – Yes
Snapshot 1.20 Pre-release 1 | Java | Windows 7 – Yes
Snapshot 1.20 Pre-release 1 | Java | MacOS – Yes
Snapshot 1.20 Pre-release 1 | Java | Linux – Yes
Snapshot 23w18a | Java | Windows 10 – No
Repro Steps
Launch the title
Go to Singleplayer > Create New creative world
Create End Portal using End Portal Frame and Eyes of Ender
Go into the End > Press ESC > Save and Quit to Title
Rejoin the world
Kill the Ender Dragon
Observe the issue
Observed result:
Ender Dragon respawns and exit portal do not open if world was Saved and Quit in End before killing the dragon. Dragon’s health bar will also appear always full, however it can be killed. If the world is exited again before killing the second dragon, exit portal will remain closed and the third dragon will spawn, so on and so forth.
Issue does not occur if Ender Dragon is killed before saving and quitting the world.
Expected result:
Ender Dragon do not respawn if the world was Saved and Quit in End before killing the dragon, its health continues to update and exit portal opens after killing it.
Attachments:
Logs
Video
Linked issues
is duplicated by
relates to
Attachments
Comments

This is not the same issue as MC-260411, since it didn't happen prior to 1.20-pre1.

Same here, can't reproduce in 23w18a.
there is more problems:
Dragon(first in the world) will drop 500 exp, not 12,000. but next dragon will drop 12,000 exp.
if you are not survival or adventure mode, next dragon doesn't spawn.
It seems related about MC-123081 fix.
It just happened to me, Im was speedrunning the game and had to go for a few minutes and when I log back into the world and kill the dragon it dies, and then immediately respawns and now I can’t kill it