Steps to reproduce

1. Create or download a behavior pack with a mob with bossbar
2. Create a world with this applied pack
3. Put the mob in the world 
4. Then, exit to the max range 
5. Enter newly to the max range 

This bug also happens with vanilla mobs with a bossbar applied by addon 

Expected results:
The mob bossbar should be shown newly 

Obtained results:
The bossbar not appears newly unless I restart the world

I discovered that this error is reproduced with any behavior pack that has an entity file with the "minecraft:boss" component and has a hud range greater than the default value (55) registered.

The inserted pack contains the entity file of the warden with said component and registers a hud range of 125 (same as the ender dragon)