[solved] Story Progression Bug - Can't continue Story at all

edit: solved, I joined a friend and afterwards i was at a different checkpoint

Hey, I was playing Slaughter with my 4th Character at early levels (after finishing Pandora Quests).
For some reason I’m stuck at the Quest “Hostile Takeover”.
I am sitting at the waypoint “Meridian Metropolex” fast travel station and am supposed to open the door to the base. But I am already sitting inside the base, with no way of reaching the door outside, to get into the base lol. Can’t run there either, since my story skipped the intro to Promethia and some doors are closed with no way of opening those.