the S&W 21-A .22LR pistol I had locked up and the slide would move only about 1/2". Sent it back and was returned with report they replaced something. Fired one mag and it locked up again, same way. Sent it back a second time and after a month finally got it back with report they adjusted the slide lock area. Very mysterious. Concluded it was a lemon so I traded for a Ruger LCR22 which has been excellent.
The action seemed loose from the start so I'm sure it was a factory lemon that got by QC.