6mm horizontal shift between image and fill layers?

Sorry, first post. Grbl controller, neje 7.5 diode laser, custom frame (linear bearings, the frame was an old expensive Commercial 3d printer). So, I have 3 layers: Image, Fill (just some text), and line. All layers look perfect on their own, but after layer 1, the laser is shifted ~6mm to the right. So layers 2/3 are aligned with each other, but not with layer 1. I figured before I bang my head on the wall too much, maybe someone has seen this before. I really don’t think it’s mechanical, but I also wouldn’t know what to look for in the gcode, I am used to marlin, so grbl is greek to me for now. I don’t see anything moving x by 5-6mm overtly, at least. Any ideas? Both first layers are 4000/s80.