Why when doing some quests (not group quests, just regular ones) with 4 of my friends in a group of 5, when we enter some areas we all end up in same instance fine, other times on same quest we end up in 2 differant instances and no matter what we do (relogging/recall to leader/etc) can't get everyone back in same instance.
I know when try to enter a 4 man dungeon 5th person can't enter, gets a message to the effect maximun number of players allowed already in. This is differant, allows all to enter just not in same instance.