Sorry in advance for the long post, but, yes, I have had the same issue, but fixed it (at least temporarily) myself.
I purchased a new Ruger LCP II with the 7 round extended magazine about five months ago, along with a couple of extra 6 round magazines.
I believe in practicing enough to matter, so I would take it to the range every few weeks and shoot 25 rounds.
The first 50 rounds, the gun performed perfectly, no malfunctions. Given that it’s such a tiny gun, I was pleased with the accuracy out to 7 yards.
The next 25 rounds, I had one incident of the magazine dropping out. I assumed, like everyone else seems to at first, that I had accidently hit the magazine release.
The next time at the range, I had started having a LOT of magazine drops. One magazine that I had installed the finger-rest floor plate on, was the worst, dropping out almost every shot. The extended 7 round extended magazine would drop about every other shot. One magazine that I left the flat floor plate on behaved, with no drop-outs.
I made sure I was not hitting the magazine release button, and noticed that whether the magazine dropped out or not seemed to depend on whether I was exerting any force at all on the floor plate either downward (curved finger rest) or to the rear (extended magazine) . The magazine with the flat floor plate did not drop, I believe, because to hold that small gun with that magazine, I have a finger underneath the magazine, so it can’t go anywhere.
After thinking about it awhile and doing some internet searching, and wanting to avoid shipping it back to Ruger if possible; I ordered a new magazine latch and spring from Ruger, and replaced those. It was a very simple thing to do, using a hemostat clamp that I had for another hobby. A pair of long, thin needle-nose pliers would probably work, too.
After replacing the magazine latch and spring, the guns shoots good as new now. No more magazine drops. But … I’ve only put 30 rounds through it so far.
Examining the old magazine catch, it appeared to be a little worn where it contacts the slot in the magazines - can’t even feel any wear but it’s just a little brightered there, like the surface treatment wore off. Apparently it does not take very much wear at all to cause the magazine drop problem to become chronic.
What I’m expecting now is that I’ll start seeing magazine drops again at any time again, as I shoot the gun more.
So here’s the dilemna: I purchased this gun for high-concealment carry (pocket carry in a pocket holster). For that purpose, I want to have high confidence in the reliability of the gun; but also need to practice with it. But, the more I practice, the less confidence I have in the reliability of the gun!
Basically, I can only count on it 100% as a single-shot! Otherwise, I suppose I could hope is that using only the flat floor plates on the magazines, with a finger hooked under the magazine, it would be usable - but who wants to carry a pistol that one has to hold the magazine up into it?
I’ll keep taking it to the range to see if starts acting up again, and if it does, send it back to Ruger next time. I did notice that the new magazine catch had slightly different dimensions than the old one, such that it held the magazine a tiny bit higher up in the well. Maybe that matters. I don’t know yet.