Stuck in Arena after boss kill; can't use Arena teleport to get out

Bug Report ID: #2621817690

I entered the boss area in the zone, killed it, and then the "Arena" portal popped up, trapping me inside the boss area and not letting me teleport out of it. It seems like the "Arena" portal popped up late, and is not designed to allow exit, only entry, to the boss. Wasted a pretty juicy map due to this bug.