OK, you're familiar with the trigger. Sorry about that, chief. That said, I still expect the major issue, since it's windage, is still you. Everyone has had occasional lapses like that.

I've never dry fired with snap caps, but virtually every self loading pistol I've ever dry fired while watching the slide has exhibited some movement-a hard fitted 1911 excepted. So long as the barrel locks up consistently with the slide, slight movement of that slide doesn't really have all that much effect or shot placement.

Since the piece is still new to you, I'd suggest more practice and see if the issue continues. Might need a few things worn in also.