Bugs like this is not on testlive only, most of 3 skull bosses do that actually, i will count up to 3 from my expirience in 1301 server
Snake - 50% : either spawns invisible, either after death just random disappear ( not helpinng even run away and back fix )
Serpentmen boss and volcano skellos well - 80% if i kill it it just disappear, most times it even not respawning in runaway back fix, it just disappear or stuck into ceilings
Red moma - falls tru ground when attacked - 90% , 10 % if lucky to kill in group she just dont have items at all or she disappears like snake