I can't get the spindle to turn on. The green power light is on and the emergency stop is released. The DRO does not display any data. What should I check to try to get it to work? It ran fine about a month ago. All axis are working correctly.

I just turned on the machine and tried the spindle . The DRO lit up and I started the spindle. I ran it up to 2000 rpm and down to 1000 rpm. After 5 minutes, it turned off by itself and the DRO went blank. The green power light is still on.

I turned on the machine about 2 hours later and the DRO turned on. I was able to adjust the RPM and I let the spindle run for 20 minutes without any problem. What would cause this intermittent problem?

UPDATE:
Today I turned on the machine and the motor started O.K. I let it run for 10 minutes and then pressed the stop spindle button. The DRO light went out and the spindle would not re-start. Out of frustration, I hit the right side of the mill head in the area of the DRO with my hand and the DRO lit up again. I was able to start the spindle and it ran O.K. I turned it off and hit the same area with my hand and the DRO would go off and then come on with a hit to the head. It seems like something is not making good contact in that area and any vibration or jolt cam make the DRO and spindle shut off. I have not opened the head yet. What should I look for as a possible cause in that area?

If I need a new spindle motor, which one is correct fit for my Syil X3 Mill?