Random Invincible Mob
Summary
So I basically have Mythicmob spawners which spawn zombies, at times an invincible one will spawn, meaning you can't kill it at all with anything, punching him won't directly hit him, it's like hitting a player with pvp disabled it'll just make some like miss sound effect also things like /mm mobs kill and /kill commands as well as entity clearing commands don't clear him, he's able to attack and act like a normal zombie as well as he doesn't despawn at all, because he has a custom name set from the spawner. The only way to fix the issue is by restarting the server. The zombie will be there except you'll be able to kill him as well as he drops regular zombie loot not Mythicmobs set ones. The big issue is they'll stack up as time goes and pretty much the server would become unplayable since there's a ton of invincible zombies in these zones.
Steps to reproduce
There's no steps to reproduce it, it'll happen randomly.
Server log file
Debug log snippet
I debugged for a few minutes but I wasn't able to paste since pastebin has a max of 500kb
Proposed fixes
If no possible fix is found maybe a mechanic that just outright deletes entities that match a mythicmob name but aren't mythicmobs.