Yesterday we started nastrond with a couple of other players.
Once we arrived to the band of 4, one of our members died and got teleported outside. He couldn't come back, so, as the last two standing, we were going to continue alone. But then i stopped to set up my deck, and a minute later i was alone, the other player had entered the 4 brother battle by himself.. somewhere else ?!? I couldn't port to him, and my battle with ymir sons had not started, yet.
We decided to meet all together outside again (porting, not leaving by the main door) and go back.
But when we entered the dungeon, the area had half reset: we still had the "defeat the 4 ymir sons" quest, but the ice wall at the beginning had reformed, the ice ceiling wasn't down anymore (so impossible to get to the other side of the chasm), all bosses had reformed, but the hammer needed to smash the ice wall wasn't there anymore.
All we could do was to leave by the main door and reset the whole area completely.
I feel it's a shame that such a long dungeon can't be re-accessed like the other ones, specially because it's quite frustrating to go there with the quest that cannot be completed.. Either reset it in full, or not at all..
Your teammate couldn't port to you? I remember specifically porting into that dungeon about three weeks ago. Not sure if they changed that recently.
Your other issues is a case of automatic realm changing. A couple of other wizards have experienced this. If you leave a dungeon and come back without porting (like via sigils), it will sometimes put you in an entirely different realm (to offset rising realm populations). The bug, however, is that your actions (or theirs) can affect each other's dungeon. I've heard of this happening in Waterworks with the levers, but your case is even worse given the hammer situation.
While I don't consider the realm changing a bug, I personally believe the group function should be revamped so that wizards grouped together will never change realms seperately (or all change together). The fact that others can change stuff in your dungeon from another dungeon should be considered a bug. I would send in a support ticket with all the specifics of what was affected and how.