New here, I have a question

My brother passed away several years ago and I inherited his gun collection, one of which was an AK-47 that had never been fired. I finally took it to the range for the first time this morning.

Long story short, it fires one round but won't cycle the next round. Called the rangemaster over, he tried it, and the same thing happened. We tried running it with a higher FPS ammo, got the same result. Rangemaster determined that the bolt isn't sliding all the way back, thereby preventing the second round to chamber up, and recommended purchasing a softer recoil spring.

Does that sound correct, and if so, can someone recommend a reliable manufacturer?

Kind of disappointing having a (more or less) "brand new" gun malfunction. For comic relief, the rangemaster (super cool old Vietnam vet) said, "Well... looks like you got yourself a single shot rifle." Yeah, thanks, man.

TYIA