Ya know i had the same problem with my yugo. Is your slant break ( I assume you have a slant break on it) tight or does it wiggle a bit? When I first got my M70 the break was tight with no movement at all and the bayo (romanian) would not lock on to the lug.... Well after 250 rounds or so the break worked itself loose a bit and would wiggle a bit. So I thought give the bayo another shot and guess what? It locks on just fine now. Maybe this is helpful to ya maybe not but that was my experience.
I found out the problem. not all romy bayos are the same. I had another 1 that fits & snaps/locks in just fine. the difference is the metal tab that moves to lock in the bayo, they are different sizes (even though the 2 bayos look identical).