I’d be willing to bet you’re hitting the slide stop without realizing it. I’ve shot one and didn’t have any problems, but that was just one.
I cannot trust any of my Glocks to lock the slide back reliably. I can only guess that it's my thumb on the slide stop. I've just learned to not depend on any of them to lock the slide back when empty.
Seriously not being a Glock guy what’s the point of the 43X, A low capacity 19 ?
It's thinner and more concealable. Its high on my list, but gets pushed back due to already having a 43 (and a 19).