Ender dragon doesn't die if it's not beside the portal

The bug

Ender dragon doesn't die if it's not beside the portal.

How to reproduce

1. Go to the end:

   /execute in the_end run teleport @s 0 90 0
   

2. Give you a powerful weapon:

   /give @p minecraft:stick{Enchantments:[{id:sharpness,lvl:32767},{id:looting,lvl:32767}]}
   

3. Attack the ender dragon many time before it will not working for the first time
   →  You see that the ender dragon does not die and it has 0 health
4. Wait for the ender dragon go beside the portal
   →  The ender dragon dies