A birt late to reply to this. I had a similar problem, same machine.

I found the relay that controlled the spindle was a bit sticky. If you activate any of the safety switches a few times it might jolt the relay back into action. Also check the postiton of the delt on the spindle pulleys, I had an issue where I was asking the lathe to spin faster than the motor could with the belt position. This resulted in the spindle error. The spindle would attempt to get up to speed then fail as it couldn't go fast enough.

Hope that helps