Today I had to relog twice at the end of a flame citadel explorer mode run, but it was impossible to rejoin the dungeon after getting back ingame. An invite message popped up and asked if I want to rejoin the group, but nothing happened. Tried relogging a few times more and the invite to the dungeon did not work. Entering the dungeon portal opened a new instance of the dungeon each time instead of being able to rejoin my group. This scammed me out of a total of 3 lootchests (15 carvings) and 2 times the 5 carvings, silver and exp reward (26s and about 170k exp).
I know this is a bug because a few days ago I was able to rejoin a dungeon where I restarted the game just fine.
1st person worldwide to reach 35,000 achievement points.