One of my players reported these bugs and I've confirmed their effect:

-Destroying the End Crystals doesn't take effect without relogging.
-If the dragon hits a mob it will go flying and get stuck in the air, and can not be interacted with.
-When the dragon flies down to the top of the bedrock portal it becomes immune to hits, and can damage itself with the fire wave attacks, it also targets at random spots on the ground rather than the players.
-When the health drops to about 60% it becomes immune to damage and starts flying around aimlessly.

• (possble, untested) The egg doesn't spawn when the dragon is killed.

Version:
1.15.1 - Paper-29
EHM: 3.14.0

Note: I don't have any debug logs on me for this

How about a config and if this occurs in 1.14.4

config.txt

Sorry for the delay, I was testing some things and my server host broke, this is the config I'm using on my server, and I confirm it does not happen in 1.14.4.

I've done some testing though and it seemed fine on a private 1.15 server with only EHM active, so this is probably a plugin conflict.

Here is a list of plugins I use, do any of these seem like they might be causing this? Cheers:

Plugins (32): BeeHivesTrees, BottledExp, Brewery, CombatLogX, DeathBan, DeathMessagesPrime, DiscordSRV, Disease, DragonTravel, EasyPrefix, Essentials, ExtraHardMode, Harbor, IllegalStack, LibsDisguises, LimitPillagers, LuckPerms, LuckPermsGUI*, Matrix, NoTrades, PlaceholderAPI, ProtocolLib, ProtocolVanish, RemovablePortalEyes, SkQuery, Skript, Thirst, TitleManager*, Votifier, Werewolf, WorldEdit, WorldGuard

No idea, I'd look into anything that deals with entities probably. DragonTravel maybe? Easiest way to test is to test a half of the plugins every time, continually dividing the current set into halves to see if the issue occurs.

This is going to take forever... Welp, might as well start soone than later!