I was trying yesterday first 4 axis machining and things goes wrong, I checked the g-code online and it looks good there. Please see attached photo and g-code file.
Link where I checked the g-code is https://ncviewer.com/
I have MK1 controller from 2011 and never tested it on true 4 axis machining.
Also X Y and Z colors are wrong in software, and the tool path is reversed on Y axis that is my rotary axis on.
Click image for larger version.  Name: cnc usb controller.jpg  Views: 2  Size: 85.3 KB  ID: 443583
And should be like this:
Click image for larger version.  Name: ncviewer.jpg  Views: 0  Size: 94.9 KB  ID: 443585