After cleaning out my Browning BL22 and replacing some springs, I experienced an issue with the lever on a regular basis. I took it apart again, checked everything, only to have it re-appear again.
Then I noticed that a small plate in the roof of the rifle’s action housing had come loose. After some investigating, I deduced that this was a part that should not move around. Especially since I discovered that I could visibly see the plate when the issue occurred and by pushing it back, I could resume shooting. Another pointer was, that this particular part does not occur in any parts list.
This is how it looks when the plate has moved then then causes a lockup:
So I decided to use some Loctite 242 to lock the plate in place and now time will have to tell whether this works or not.