Thanks so much for the response. I did compare mag catches. Fairly complex surface, not the easiest to inspect for wear. Anyway, OEM magazines working properly (does not drop) leads me to believe the issue is with aftermarket Mec-Gar magazine.
Perhaps this link to the videos will work:
https://photos.app.goo.gl/d5kGv4smgf7ELJBEA
I struggle with linking to photos in my Google drive. Used to be easy to set Google drive folders to "public"; that feature appears to have been removed. Testing links doesn't always work, since being logged into Google drive masks sharing issues.