I joined the forum so I could reply to this thread.
Just got a Shield .380 EZ last week. 1st 59 rounds had the last loaded round in the mag eject without chambering about 50% of the time (I was loading about 5 rounds per mag). Gradually to round #300 the last round malfunction got down to about 20-25% of the time. Both mags. Nothing made it go away, not different ammo, cleaning, different shooters, or different lube. To not waste as much ammo, I had resorted to only loading 2-3 rounds since it was always the last round that malfunctioned.
Pondering the situation, I wondered if the mag spring was too weak to hold the 1st round loaded firm enough to handle the slide face hitting it and thus go right into the chamber. It was ALWAYS the last round in the mag that would eject or sometimes stove pipe.
Taking both mags apart, I inserted a loaded .380 round between the bottom of the mag spring and the floor plate, thus changing the 8rd mag to a 7rd and putting more pressure on the mag follower for the first round loaded. Loading the mags with 2-3 rounds and firing (after all, it was always the last round that didn't chamber), I went through 10 "mag cycles" (1 mag cycle = load rounds in mag and fire until empty) with each mag with no malfunctions! Statistics would have had 4-5 failures in 20 mag cycles, but I now had none.
I will be doing more testing and have 2 more mags arriving shortly. I'll then contact S&W. At this time, I'm convinced, at least for my pistol, that the mag springs are too weak and thus do not hold the 1st round loaded into the mag firmly enough for 100% functioning. Of course S&W made the mag springs weaker to make the mag EZ to load. I'm thinking the mag springs are right on the edge between too weak to function 100% and making the mag really EZ to load.
Watching Shield .380 EZ review videos, I saw the same last round malfunction in a couple of videos. The reviewer really didn't ponder the problem, but simply cleared it, reloaded and went on. Even the American Rifleman review mentioned the last loaded round eject or stove pipe and didn't realized there is a problem, thinking it was a matter of breaking in the pistol.
Of course now my pistol doesn't have all the features as advertised (8rd mag), but on the other hand it still holds more .380 ammo that my previous carry pistol.
Otherwise, it's a joy to shoot. I love the lightweight and mild recoil.