Dishwasher Repair. Dishwasher is a Stoves/Newhome DW616Rotating spray arms do not always

Question

Dishwasher is a Stoves/Newhome DW616Rotating spray arms do not always operate.This is an intermittent problem - will sometimes work normally for a few days then arms will not move at all with no water coming from them. Machine appears to go through its normal cycle. Some times cycle starts normaly and spray arms stop working part way through.