I have recently noticed that several of my 10rd Magazines for my Glock 23 .40cal have been dropping after the first shot. I discovered that the magazines that drop out are slightly different from the magazines that function properly and I am wondering if these are the wrong magazines for the pistol or defective in some way. I am attaching pictures of the two magazines and am hoping someone can shed some light. I have done a lot of research and I am coming up empty handed. The working magazine is the one on the bottom of the picture compared to the top magazine that is dropping after the first round. The working magazines have a 1 on the follower compared to a 5 on the ones that drop out, there is also a slight difference in the shape on the upper side of the magazine where it locks in the chamber as seen in the pictures. Any help in identifying this would be greatly appreciated.