Help. K40 laser machine engraving crooked

[Claireck]

Hi, please help
I’ve been using my k40 Chinese laser engraver for over a year now and have only recently come across this issue. The machine plays up half way through engraving. It begins to engrave the image indented. I’ve tried engraving multiple images and the same ’indenting’ occurs. I’ve checked and cleaned the rails, pulley, belt, mirrors and lens. Could a possible lag on my laptop during engraving cause this problem as my laptop freezes at times and is very slow?

Any suggestions would be greatly appreciated. Thank you ~

I’m engraving at 400mms at 13m/A.