Fractal world is full?
Did you kick anyone from the party? Sometimes when a person is kicked they end up staying in the dungeon. Then if another party member dc’s or leaves the dungeon to repair or something, it will give you this error as the dungeon already has 5 in it. Moving onto the next shard will kick the extra person from the dungeon. Although they will be able to troll you until then.
Nope! Entirely new parties both times.