You did the right first step, buying more magizines. As said, Tapco mags are great b/c you can file them down if need be to fit properly. If that doesn't work, keep tryng mags... maybe some other surplus metal mags will work.
This is interesting, I own two Century Arms AKs and they both fit a variety of magizines with no issues with functioning. Some may have more play than others but not to the point of malfunctions. If the magizine swaps don't fix it, can you send it back? Perhaps a local gunsmith can look at it?
For those who fight for it, life has a flavor the protected will never know.