Bunker doors won't open again after getting killed inside.

I cleared out everybody above ground, including all flying drones, grabed all intel /collectibles / chests and went on to the bunker without raising any alarms. I opened the bunker main door down the ramp (used keypad, front door slides open), went inside an got killed in the second room.
I respawned in the office building. As the guards and drones also respawned, an alarm was raised by a drone, when I left the building. Anyway - I killed everybody above ground again and went back down to the ramp. The keypad could be interacted with again once (press "E" to open), but the doors stay closed. I can't interact with the keypad anymore and I do not get any hint that something is amiss. (I even tried placing a body near the door just to make sure, but as expected that did not help either.)

So I thought - okay, an alarm was triggered, maybe they went into lockdown and this is on purpose. Let's see if we can find a backdoor...
I went to the woods behind the complex, found a downstairs "garage" and a recon grenade told me that there are badguys just behind the wall. There even is an ungrated ventilation shaft that looks suspiciously welcoming and familiar from so many other stealthy games. But I can not climb into it - very disappointing.

So I went back to the main door again, just to check again but to no avail - still closed, keypad inaccessible.
That's when I decided to fast travel to Erywhon, report this as a bug and have breakfast. ^^

Now I will try again...