Random vertical/horizontal lines

I’ve tried a few times CNCing some text for family on a plate. However, at some arbitrary (and non reproductible) times in the drawing, the RAMPS seems to command a vertical (down) or sideways (left) line before coming back and continuing the print as if nothing was out of the ordinary.

Since the locations where the lines appear differ from one “run” to the next, I suppose it’s not the gcode (generated with ESTLCAM).

Did anyone have this problem ?

loose wire, bad usb connection? If you use a USB and your computer turns off the screen that can happen.