Unless you are unknowingly riding the slide or the slide lock down with your thumb due to grip placement, or simply limp wristing. I would think it has to do with magazines, either magazine springs, followers, or possibly with the pinning of the magazines affecting the magazine spring/follower travel.
Do you know when your pistol was manufactured? I have the Staccato P optic ready that was also purchased a few months before the ban was announced, mine did not come with any spare recoil springs. My pistol came shipped with the no paint recoil spring for standard loads, and I bought the same springs for spares. I also have bought 4 more pinned magazines from Freedom Ventures after buying the pistol 2 with the extended base pad and 2 with the standard base pads. I have never had the pistol not lock back for me with any of the magazines I have, and Im at least 2000 rounds into it
If it was me I would clean and lube the pistol very well, specifically the rails and the slide lock, and try racking the slide back slowly with no rounds in it and make sure it locks back with all your magazines easily.
Dissasemble your magazines clean and lube the springs and just check how well the springs function in moving the followers all the way to the top
Shoot it with your thumbs off to the side making sure not to ride the slide or slide lock, to rule that out
If possible try to use someone elses magazines in it to rule out your magazines
As others have said I lean towards the magazine, if you can rule out the shooter/grip 100%. As personally the only issue I have ever had with my Staccato or any of my other pistols not locking back have been when I let new shooters try them and they either ride the slide or slide lock with their grip, or they simply limp wrist when shooting.