That's the strange part I haven't done any changes to the electronics, except I changed to shielded signal cables between the VFD and the controller. The stops are very random in behavior, but it seems to increase in frequency when I use the machine. And the next day it runs for a while in the beginning, and then the frequency between each stop becomes shorter. However I haven't run the machine enough to be absolutely certain this is a recurring event.

That the problem increases with use would correlate with temperature increase. But the VFD seems cool. The 2.2Kw spindle becomes a bit warm, cooling water at 44 degree celsius, but I dont see how that should trigger and overload error.

The randomness of the failures could just mean noise in the electrical system. I tried disconnecting the control cables from the controller to the spindle and setting speeds, start and stop from the VFD. I haven't had any problems since, but I haven't tested it for long enough to be certain.