Another party bug.
I was in a full party of 5 inside a dungeon and got an invitation to another party.
I thought it was impossible to receive another party invitation while in a full team but 5th blinking portrait just showed up stating the invitation.
When the invitation showed up I got kicked out of the dungeon being still in my party. I ran back into the dungeon. The invitation was still there so I decided to reject it since I had a full party already. The second I hit reject I go kicked out of dungeon again.