Recently while doing the Seer Marino arc I encountered a bug in two of the missions, the one to steal intel from the Legacy Chain and the one after that, where the mission door assigned was the doors to the Arachnos building in Mercy, which wouldn't let me into the mission- when outside, it led me in, and when inside, it led me out. The first time I autocompleted the mission hoping it was a one-time thing, the second a GM (I think) changed the mission door to a working (and more fitting) location. It's been resolved for me now, but it may happen again to someone else.