This really isn't a bug maybe but is annoying. If you are dead on the last boss fight when the boss dies you get teleported out before you can loot the boss. Not sure if that happens after other fights as well but you do get teleported before getting to look around.
I was able to run back through and loot the last boss but still kind of annoying. Might be nice to have just a little more time before getting teleported.
Just ran this on vet, and the final boss DID teleport with us. Someone who only partially looted it could still finish looting afterwards.
It sounds like it was your run that was bugged. I hope it behaves better in the future!