I recently bought two Glock 43x pistols, one MOS and one non-MOS. I shot the MOS and it was not resetting the trigger during live fire. During dry fire it was fine. It felt a bit odd as well. I took it to my armorer and he found the slide guts were coated in too much oil and the frame guts were completely dry. I had him check the non-MOS, which I hadn't fired at all, and it was similar but not as bad. He did verify everything was together correctly, nothing was broken, etc, so figures the lubrication was the issue. I haven't had time to live fire yet but hope he's right.
Per him, since Glock quit using the copper colored anti-seize he's been seeing a lot of that sort of thing with new out of the box guns. Apparently they've hired some very minimally trained people to assemble and lube, again per him.
Side note: This reinforces the need to test fire anything before you carry it for real, even "Perfection"...