Bad cut on second pass

Hi all, new to this forum thanks for having me - I have been using epilog engravers for about 7 years now, I have started my own business and i picked up a cheap 40W engraver from china via ebay (i think its a k40 copy?)- just to do the small jobs that i am not out sourcing.

Im running it via coreldraw all is good and been running it for the past 3 weeks - Normally i have to run my job to cut 3 times as too much power burns my 1.5mm thick material leaving a bad finish on it (i make labels for the electronics industry mainly panel boards)

today when cutting on the 2nd and 3rd pass it moved slightly so it didnt cut in exactly same place id say about 0.3mm off each time, so far ive cleaned all the mirrors and lens with lens cleaner and wiped over the rail and this hasnt sorted the issue, the machine hasnt been jogged or moved in anyway while cutting, any ideas please?