We killed Nexus Princess on Heroic Difficulty, Nerub’ar Palace, but after the fight we were still en an encounter.
We could not release or combat ress - so the rest tried to die.
Nothing helped, we tried to invite an outside healer - but you cannot enter with an encounter in progress.
Princess won that round then.
Hey Dezzie,
I’m sorry to hear this and while I understand it’s probably of little comfort, you were not the only raid to experience this.
No specifics just yet, but we’re aware and taking a look at what might be going wrong here:
So… How do we get out?
According to their linked article … it’s fixed 
Our developers have fixed the issue that was causing this problem. Please try again.
If you’re still having issues, time to put in a bug report/raise a ticket.