Cutting problems on a gerber

I've had the gerber doing test cuts on lots of different materials & all seemed to be progressing well until yesterday when I decided to try something a bit more complex.
Had a file for a motor mount which I was going to cut in aluminium at some stage but decided that would be a good test & rather than use ally used a bit of MDF to see how it would turn out.
Things seemed to be going well, the machine had already completed 2 full passes but on the 3rd pass it went a bit haywire & went completely off track.
After stopping the machine I sent it back to the zero co ordinates & it was miles away from where it should have been.Attachment 8988

first guess is your rapid is to high and it dumped a shitload of steps moving to zero at whatever rapid you have set up at ready for its 3rd pass, however, looking at the photo it looks to have lost steps equally in two axis so it may well be something a tad more elusive

maybe the draw on your power supply is getting close to its limit with two axis at full speed?

if you have set your rapid speeds by pushing one axis at a time to its limit then backing off this problem would have stayed under the radar
its worth having your machine zig and zag at full belt then see if it returns to zero

Mark, thanks for taking the time to reply, at least I have a starting point to try & work from now.