Hotpoint Aquarius WMA46 – Machine switching itself off

I have a problem with my WMA46. If I put it on Fast Spin cycle, the waste pump runs and the drum starts to turn. However, during the 2nd revolution of the drum, the pump stops running and the machine just shuts down.I have checked the machine for blockages and it is clear.The tube from the pressure chamber to the pressure switch is clear.I have checked the main control board for signs of damage and signs that something may have burnt out but found nothing.
I have checked for an error code using the error code tables on this website and I get A=lit, B=lit, C=lit, D=unlit. Your error code fault table suggests “Tacho Error on Main Drive Motor”. I’ve checked the Tacho and wiring and they seem to be ok. I’ve checked the carbon brushes and they are fine. I’ve conducted a continuity check along each wire from the control board connector to the motor connector and found no breaks in continuity.
I’m tempted to purchase a new motor but as it seems to run, albiet just for a short time, I’m not convinced that this is the solution and could prove costly if this doesn’t solve the problem.
Is there a test I can do on the Tacho itself to see if it’s defetive? Or can anyone suggest what else might be causing this to happen?
Many thanks in anticipation