The way it was explained I have three moods shirt to me if your grip is like a vise you can slap the trigger any way you want and the gun won’t move. Start with your grip. If it was your sights you’d have tight groups. Well, I’m no expert, but I’d say first thing’s first: you should bring the target in closer so you’re landing on paper. Then you can see whether or not you’re at least consistently low/high/left/right. It could just need a sight alignment and hopefully, your assumption of which direction you’re off by is incorrect. Either way, bringing the target closer will allow you to land on paper which will answer some questions.
I have a Sig P938 also I have three moods shirt. The trigger pull on mine improved after a few hundred rounds. I would recommend doing some dry fire practice. Here’s a good drill to start with I suspect that with the striker fired pistols, you are using a six-pound squeeze on the grip, and a six-pound press on the trigger. But that on the P938, you are using a six-pound grip pressure and an 8-10 pound trigger pressure. When you press the trigger, you might be moving the pistol off the target.
Honestly, if your driving nails I have three moods shirt with a shield and a G43 at 15 yards maybe just sell the P938. There is an improbable but non-zero possibility that you have had two defective P938s in a row. To eliminate this possibility, have a shooter of known ability shoot your pistol. Find the shooter at your range that is consistently punching out the X-ring of her target.