Ariston SWD1000 washer/dryer motor problem

The motor is a Indesco 940N21.01. The symtom is that when the machine has to go on spin cycle, it is quite happy on the low speed pre-spin cycle, but when it gets to the time to go onto high speed, there are sparks that are emitted from the brushes and it gives a small bang as if it wants to do it but something is fused and reverts back to slow spin. The operation is re-tried about 5 or 6 times as there is a censor on the motor that high speed had not been obtained.
I have changed out the brushes with new ones as this was the obvious thing, but it made no difference. Are there any other things it could be? well apart from maybe a winding wire on the motor broken and not quite making contact! I would be really happy if anyone has any pointers to the problem. I can’t describe my disappointment that the brushes swap-out made no difference!
Cheers
John