I have been able to reproduce this on my office computer connected to a UC100 and have just tried on my working machine, it still does the same on that computer. I've loaded the "raster drills" file from example codes and temporarily placed a "save settings" button on my run screen.
On first loading and running the file there are no issues at all, but if I press "save settings" and then hit cycle start the program runs correctly for a few lines but then seems to go completely off course. In the included video it circles up and back to near machine home then starts slowly returning to drill again after missing several holes.
Other files have the machine circling away from the cut path with the Z dropping continuously, which would have been quite nasty had I not been air cutting..
If there's anything you guys need me to try, let me know.
https://goo.gl/photos/Prq6nUaNLUgcWXzLA UC300ETH
UCCNC 2037