Co-op bug?

I was trying out the public co-op when I joined an existing game. The player who owned the game and I were both already in the last chapter of the beta and were heading into the Skeleton King's crypt. Another player joined into the game soon after and we all went into the last level. Everything went fine until we got to the room before the Skeleton King's chamber. I went ahead and tried to go in and got the message that if I went in, everyone would be teleported into the chamber. As such, I hit cancel and waited for my companions. However, once the game owner got in, the other player went in with them but I got stuck outside. I got all the messages from events being cleared, such as "Find an Alternate Path" and "Put the Crown on the Skeleton King" but I was stuck outside. After they killed the king, the chamber became accessible but asked me to start the event again. Once I got in, the king was already dead but there was nothing there. No drops or anything.

Sooooo, I'm not sure if this is actually a bug or if bosses are intended to be kept at 2 players for the Beta. But I'm sharing nonetheless. =]