LOL (inside joke)
IMO, Sounds like your slide is moving very fast and the Mag spring is not moving the rounds fast enough. It's doing it on the last round because the spring is at its "least" coiled state, less tension.
How to fix it is another question, putting more tension on the spring may cause other problems. Stretching the spring is out of the question.
Try using the FMJ Winchester ammo or Federal ammo and see how that works.
BTW, I don’t have any pistols that are LEM models. In fact if it says LEM it’s a warning label for me to not purchase the gun…….
TS