It happens ONCE, but was somehow frustrating: A group of 3 players, made before entrance; we entered, but one of us (not me) was not seeing the two of us, neither the two of us were able to see the third player, but all 3 were indeed inside the dungeon.
Has that occurred to anyone else?
Re-logging was useless, for that third player (was not changing anything, except that seeing that he was offline for a short period),
Note that this dungeon was part of a quest, it was the last step, killing the boss. The previous steps of that quest were multi-players, but that last step was dungeon-like (no player of other groups were visible).