Problems transiting between carves

Only really just starting to use my Stepcraft 420. I've got an order for 200 fish from 6mm MDF with an eye cut in each. Seemed simple enough until the Stepcraft started cutting the eye in the wrong place!

The file is created in VCarve Desktop and I've checked and rechecked it and there are no phantom layers, vectors to tool paths to cause this problem. I recreated the file from scratch more than once and still have the same problems.

Getting nowhere with VCarve I next started delving into the GCode it produced. The problem always seems to be in transiting from one area of carving to the next so I checked the transit code and it all looks OK as far as I can tell with a very basic understanding of code..

I then created a test file which I haven't tried to actually carve but ran on my machine with no spindle. The problem became clear that on occasions the machine would lift from one carve and not transit correctly to the next carve, almost as if it got the X and Y axes confused, or it simply stopped in mid-transit.

It only ever happens on transit between carves and never in the middle of a carve itself. You can see this on the video at 2.02 and 2.59 on the video listed below.

In the GCode the problems occur at lines N12010 and N17940

I’ve now convinced myself that the problem is either with UCCNC or the Stepcraft machine itself, but no idea which!

The GCode file is here: https://www.dropbox.com/s/4qu4kuy1x7ii3i1/Test%20-%20six%20fish%20one%20pass.txt?dl=0
The VCarve file is here: https://www.dropbox.com/s/eql02cdch7ucd46/Test%20-%20Six%20Fish%20One%20Pass.crv?dl=0
And a video of the Stepcraft doing the carve is here: https://youtu.be/bJfUWa6mGBU