How old is the hammer spring you're using? The reason I ask is that I have a penchant for used guns. And I've seen in a number of them that function can improve dramatically by changing springs. The most recent being a Walther SP22 (not a P22) that went from running really well to suddenly having A LOT of light strike issues that weren't being resolved by deep cleaning. The firing pin imprints certainly looked adequate, and yet maybe 2-3 resets would set the round off, or fire in a different gun without issue. Still feeding and ejecting fine, just not firing reliably.
I got as many new springs as i could, including the hammer spring and it went back to 100% function just like that! The FP dents don't look any deeper, but there must be a bit sharper impact at play that takes care of it.
I let myself get distracted for months by everything that it wasn't. I learned a lot more in-depth stuff about that pistol than I'd have ever imagined, but there it was, once again, a very simple fix to to a very simple problem that was not easy to quantify. Moral of the story, when in doubt, if there's any sort of age on the springs, remove that doubt, even more so when there's nothing mechanical evidently wrong.