@ubiwan I just followed the steps in the FAQ and I keep having the same issue.

The first few times the bug appeared I didn't fast travelled or start a different mission in-between. I followed the logical order of events. The only 'strange' thing is that I didn't managed to keep the low profile and had to kill several poor enemies, but nothing else. When I approached the Buckingham longhouse, it popped the 'try to force the door open' message and then I tried and didn't work. Then I stepped back a little and the short dialog between Eivor and Sigurd started, which made me think that it was an only time bug, but it appeared again, and again, and again. So I'd tried different things (starting a new mission, killing all the enemies, going away and then coming back, burning the longhouse down, ...) but none of them worked.. And here we are.

@ubiwan yes, but the bug had already appeared several times before, so I used 'raiding' as a last resort (that's what you can see in the clip) in order to open the door, but the crew didn't even disembark.

So yesterday I was finally able to "avoid" the bug. It wasn't a painless solution, I warn you.

After several hours of trying everything (restarting the mission, killing them all, burning down the longhouse,..), even with the inestimable help of @UbiWan (thanks again), I just gave up and started other missions, mysteries, etc. BUT I just kept feeling uncomfortable and something told me that I needed to restart once again. That is why I came back to the previous mission, the Londen final, finished it and then restarted the Brewing Rebellion mission again. YES, this erased hours of game, and it was heartbreaking, but also worth it. Here's what I did differently this time:

1. I didn't had any more missions going on at the same time, besides those which are inevitable, you know. I finished everything I could before starting BR.
2. I didn't kill any enemy before arriving to the longhouse: low profile all the time.
3. I waited for every animation to finish. When I approached the Buckingham longhouse, it popped the 'try to force the door open' message up and then I waited (without touching anything or even moving) for Sigurd and Eivor to finish their dialog and then for Sigurd to make his move of asking for help, etc. I didn't do any of those things the first time: I tried to open the door right away I arrived to the longhouse.

I lost several hours of game, but at least now I can go on with the rest of the story. I hope this is helpful for you!

@ubiwan I just followed the steps in the FAQ and I keep having the same issue.

The first few times the bug appeared I didn't fast travelled or start a different mission in-between. I followed the logical order of events. The only 'strange' thing is that I didn't managed to keep the low profile and had to kill several poor enemies, but nothing else. When I approached the Buckingham longhouse, it popped the 'try to force the door open' message and then I tried and didn't work. Then I stepped back a little and the short dialog between Eivor and Sigurd started, which made me think that it was an only time bug, but it appeared again, and again, and again. So I'd tried different things (starting a new mission, killing all the enemies, going away and then coming back, burning the longhouse down, ...) but none of them worked.. And here we are.

@ubiwan yes, but the bug had already appeared several times before, so I used 'raiding' as a last resort (that's what you can see in the clip) in order to open the door, but the crew didn't even disembark.

@peronella Here's the clip of the issue:

I have the exact same problem. Retrying the mission doesn't work, either.