Quest progressed without my action (Golden Door Idol), followed by instance crashes

Bug Report ID: #828342276
I was in the Ziggurat Encampment with the Idol in my inventory when suddenly it disappeared and my char spoke some banter about entering the Kopec temple.
Then I went to the temple to try and enter it, the door opened on its own, but trying to go trough it resulted in "failed to join instance" error - back to login screen. The same error then stopped me from getting back into the game a couple of times. When I finally got back in, went down to Kopec temple, tried entering. Same error, another failed retry to join the game, when I got in I tried CTRL+clicking into a new Kopec Temple instance, still got the Failed to join instance error.
Gonna try again in a sec.

It worked correctly after several minutes and tries.