I picked up an early S&W Model 41 from an estate and sent it to my son in Texas. He's used it a few times successfully, but the last time out began having trouble with the slide stop. They fired off a full magazine, and after reloading they were in the middle of the next mag and the slide locked back and won't release. He can take the gun apart and put it back together, but when the slide is pulled back again it locks open and won't release. He's a thousand miles away so I can't see it and have never owned one so don't know what advise to give.
Can anyone help?
Thanks

Have him check the slide stop spring to make sure it isn't broken or missing.