Looks like I managed to hit a progress breaking bug by glitching behind 'The Castle' wall before actually unlocking it quest wise.

I had several enemies on the street in front of the wall, of which 1 decided to take cover behind the castle wall. I made the mistake to follow, which got me stuck on the other side, as you can't get back over the sand bags from that side. So I had to use fast travel to get away. It might be that getting behind the wall unlocked 'The Castle' as a fast travel node for me, at least, when I used it as it was obviously the closest to my location, I ended up inside the castle, next to the corn field. Looking around, all entrances were closed and I only noticed a quest marker sending me down into some bunker/basement. A cutscene played, after which I was put back into the still locked down castle. I fast traveled outside and just continued playing as usual until I now I have reached the point at which I have to regularly enter the bunker, which obviously has already happened and I'm therefore now stuck at this step with no obvious way of fixing it.

TL;DR version on how to recreate:

1. Be at 'The Castle' before you are actually supposed to enter storywise
2. Climb over the wall (location, see screenshots)
3. Run around behind the wall.
4. Fast-travel into 'The Castle'
5. Follow the marker to the bunker/basement and enter.
6. Cutscene plays
7. Fas-travel to a location outside the castle
8. Continue progressing until you are sent to the castle
9. Be stuck with the 'Speak with Alani Kelso' quest step
10. Be sad

Screenshots: https://imgur.com/a/bchq5bq

Would love to hear if this has to be patched or whether my quest progress can somehow be reset to the point where I can enter the basement.

Cheers!