[Herb]

Hairy, about the only thing I can come up with is the possibility of the magazine catch spring being broken allowing the catch to recede too far into the frame thereby causing the magazine to hit it rather than slide past and lock. To check this press on the mag catch and notice if it goes into the frame and then pops back out when the pressure is removed. You can also check this spring by carefully removing the left grip panel, it should be clearly visible above the mag catch. Be careful with this left grip as they have a habit of cracking right where the safety lever is.