I have three Glock 9mm's, a G17, G19, and G26. All are good shooters, no jams, or failure to eject. For the last six months or so I have had problems with the slide not locking open on an empty mag on the 19 and 26, but never the 17. Various mags, different FMJ ammo, and I have never had the problem when shooting up deffensive ammo thats a few months old. Any ideas?