The Bug:

The ender dragon fight does broken after re-join the world. there's some broken stuffs.
If I defeat the dragon, another dragon spawns immediately. (but it is only while survival mode, if you are creative mode, dragon doesn't spawn) and this dragon fight does works properly.

I think it is related about MC-123081 fix. I can't reproduce it in 23w18a.

Steps to Reproduce:

1. Enter the end dimension.
2. Wait for until the dragon has spawned.
3. Save and quit the world.
4. Join that same world.

Observed Behavior:

• Dragon boss bar doesn't update properly, it is always full. but still I can defeat the dragon.
• If dragon is died, it doesn't create end portal, dragon egg and new end cateway.
• If dragon is died, and it does spawn new dragon immediately if player is survival/adventure mode.
• If dragon is died first in the world, it will be drop 500 exp, but next dragon will drop 12,000 exp.

Expected Behavior:

• Dragon boss bar does update properly.
• If dragon is died, it will be create end portal, dragon egg and new end cateway.
• If dragon is died, it doesn't spawn new dragon until place 4 end crystals on end fountain.
• If dragon is died first in the world, it will be drop 12,000 exp.