That’s definitely a timing issue; which I believe is what the OP is most likely dealing with. I’d contact Apex for their guidance. I’ve read that there’s a “loop” in the trigger bar that sometimes needs “adjusting” after some of their components are installed. I’ve never had that problem myself; but many others have…I had an issue on a 1.0 FS M&P 9MM. Well, two problems.
One sounds similar to yours. Small indent on the primer but not firing. Happened 3 or 4 times per magazine. Timing issue on mine. The striker block was not being moved completely up/out of the way by the arm on the trigger bar before the striker was released by the sear. The striker would hit the striker block as it went forward (sometimes) and that would slow the striker down enough to keep it from lighting off the primer.
I think there used to be a video on the Apex web site that explained how to fix that (what to adjust and check).