I'm thinking there is enough looseness/slop in this rifle to keep the bolt from engaging the block as deep as it should. With the block edge being rounded off like it is the bolt is getting close to being able to ride over the block rather than staying locked in battery.Happened to mine, too. Not quite that bad, though. You can get spare parts from SSD/Germany.
With the block edge being rounded off like it is the bolt is getting close to being able to ride over the block rather than staying locked in battery.
Pete
Not only that, I think the wear has already increased head space beyond safe limits.
How did you get the block out of the trunnion? Did you manage to pull out the pin holding it in place? Did you need to remove the extractor to slide the block out?