This one has me stumped. I've been shooting all manor of Glock's for 15 years without issue. 3 months ago I picked up a G20SF and a G29SF new. Great guns. But I have developed this strange problem in both guns. The gun will go to slide lock with one round still in the magazine (any of a number of mags). I can pull back on the slide to feed the round but it's at slide lock just as though the mag was empty. It happened 3 times this morning with the G29 SF. At first I thought my thumb was hitting the slide release during recoil but that is not it. If the nose of the bullet points up a little bit in the mag, it will allow the front of the mag follower to rise up enough to engage the slide stop lever . This is with both guns, only on the last round and the guns run 100% otherwise. Both guns are 100% stock save but the G29 mags have the Pearce +0 extensions on them. It has happened with factory and reloads. I shoot mostly reloads though. Any ideas guys? I emailed Glock last Monday but have not heard back from them.