Broken firing pins?
This ^^^Another thing is striker fired guns don't have a hammer to create a mechanical opposition to the initial rearward travel of the slide. When a hammer is in play, that hammer acts like a lever to soak up some of that extra energy. This can change the timing of the unlocking and reduce primer drag.
I just bought some once-fired factory load .41 AE brass and the primers showed evidence of this anomaly. And that probably happened 30 years ago. I know of no .41 AE Glocks, so it must have been some other firearm. It may be associated with the stamped/flat metal firing pins that leave their "Glock-like" narrow impression on the primer.Primer drag usually indicates the firearm is, in case of semi auto handguns, unlocking early as the firing pin is still outside of the firing pin channel as the barrel starts sliding down in the common Browning action guns.
I think this topic has become huge because of MACs video on the P365. I have to disagree with MAC that no other handgun shows primer drag other than the P365.
I had this happen years ago in a 1911 that I'd had since I was a teenager and had fired unknown thousands of rounds through. The problem vanished along with the severely worn and weak recoil spring that I replaced.