Hi Bob have you checked the chain and sprockets on the pump and motor for a little play but not too much. Also have you checked the spindle motor and belt for tension to make sure it isn't slipping er rubbing on edge of belt on its track. Give if a run with bottom cover and chain cover off but keep fingers clear.

David

Why the question mark Bob? Just channel the Monty Python parrot sketch as you look at it and hope it's sleeping (it isn't, it's a few minutes from letting the flames out of it to join the smoke).

It can be almost impossible to detect a shorted turn with a resistance meter. If you have a meter that measures current, then measuring the current to the motor on each of the three phases is more likely to detect a winding fault. Ok, it'll need three goes at disconnection-meter connection-reconnection, but it will show if there is a poorly phase on the motor.

Before you start this, is the grinder being fed from a good balanced three phase supply or a static or rotary converter? If the latter two, are the phase voltages reasonably balanced or is the generated leg much higher than it should be?