My F1 seems to have an issue, When I draw a perfect circle that is 25x25mm it engraves as a oval that is about 25x29mm. I didn't have this issue when I first received the machine a few months ago. The F1 has had a few firmware updates since then though so I don't know if one of them has messed things up or there is a problem with the F1. Does anyone know how I can fix this issue?