Take one of your other barrels that work well, and swap out the barrel locking lugs and see what that does.
Whatever you do, don't send your frame back to Fred at Bullberry. That whacko will end up telling you your frame is junk, then he will scratch the life out of it with his tools trying to make his barrel work, then send it back to you and tell you he never touched your frame! (YES......true story....it did happen to me!!!!)
Dave