It seems that the main problem with this pistol is with the magazines. From what I've read, the ProMags work better than the originals. And so it is with my originals, they do not lock back. It is clear that the follower does not engage the slide lock as it should. Called SCCY and they are sending me two (2) replacements, no need to send the originals back. Mind you, the original mags feed fine, no misfires, no misfeeds.
So I tinker with the originals and find something that might seem counter-intuitive. After trying some common "fixes", it all boiled down to a couple of things. One, bend very slightly upward the top coil of the mag spring and rotate 180 degrees the mag plate insert. Voila! Follower pushes up and engages the slide lock. However, to make certain I ordered a couple of Lakeline's 10%+ Sig P365 magazine springs that should give it an added push. Should be getting them today.
If push comes to shove, I'd say that rotating the mag plate insert did the trick. Gut feeling told me that that might work. Can't say why, it just did.