Quote Originally Posted by PotatoMill View Post
I haven't had any problems since, but I haven't tested it for long enough to be certain.
Until you test adequately any answers would be guesses, or would be requests for you to test adequately ;-)

Motor overload should be related to current draw as read by a current sensing circuit so the error ought not to be generated by input noise.
Have you checked that the current Parameters are correct for your spindle?