Mobs still showing even though I cant kill them

I got this a lot in LPQ when other players would kill boxes or mobs. A full system restart fixed it each time tho (same fix as buggy hp bars).

 

Can confirm that this happens sometimes at skeles, used to happen all the time back when the server had to be restarted every 2 days, so might have something to do with memory.
Usually it's fixed by everyone who is in that map leaving it (ccing works), it also happens with drops, where they become and "Unavailable for looting" but don't dissapear until you cc, log off, etc.

 

Seems to only happen at ToT (coincidentally also at these maps with the green-coloured hat wearing mobs).

Happened to me 2-3 months ago.

 

Happened a few times at skeles to me, but not recently. It still does happen with item/meso drops from mobs tho, when some1 else comes in the map and does damage(over half the hp) to mobs before leaving then the items/mesos stay in the floor and can't be looted but they don't go away either.