Those guns are known for taking a bit to break in, and then running anything afterwards.
The slide is stupid light, the recoil spring is very light, the mag spring is very hard for its size.
Any imperfections, roughness etc, take a bit to smooth out, and a light slide and recoil spring won't overcome those little imperfections the way a full sized gun will. The mag spring will weaken and finally not push up hard enough to hit the slide stop.
My LCP original took 250 rounds. Had the same hiccups yours is. After that, it's been through over 2,000 rounds of everything and not a single issue. My son's LCP II just got broke in last week. It took 150 rounds. Now it eats anything. My best friend's LCP Max didn't take but 50 rounds, but he sat in front of the tv and racked the slide a few hundred times. My ex wife's took about 300, not it eats anything.
They all had little issues early. Most were failure to feed or eject, one or two every few mags. Slides locking back when the mag had rounds in it, and my son's didn't like to fully chamber a round from empty with a fully loaded mag, and would lock the slide back with rounds in it. His stopped having issues last week after the second mag he fired through it. From there he put 50rds of crappy Wolf steel through it, and 40rds of Winchester flat nose.