Had same thing tonight for several of our party members (I think 4/8 during different fights, one of them was tank which was fun). Had also an issue where it didn't let us in the instance because we didn't have 4 party members (yes it was hardmode we were trying to get into).... Same server too, though I don't know if it makes a difference. Getting really annoyed with not being able to run late night events (starting to get lag after 8pm UK time).