the only issue I had with a mag not locking in a AK was the MD ARMS 12 ga SAIGA drum. had to barely take a bit off the top of the rear mag "stud" so it would lock in.
if you take out the bolt group completely out of the AK and view it from the top as you put the mag in, you'll see that the there will be a piece of metal at the rear of the mag well that is stopping it from fully seating in the mag well and locking in. just go super slow to take a bit of material off the top of the stud on the magazine. don't get too aggressive. just a bit will do. check for fitting often.