The dishwasher makes a terrible grinding or shuddering sound between wash and drain as well as between rinse and drain. It goes through a complete cycle and cleans the dishes, but something is clearly not right. During wash and rinse, the water goes through all three spray arms, and there is no noise; during drain, it drains correctly, and there is no noise. It is only between cycles that it makes this noise.

I have already replaced the drain pump, the diverter motor, and the drain hose (as well as the turbidity sensor); nothing has helped. What should I replace next? The two remaining options appear to be the main motor/pump and the circuit board.

The dishwasher is a Whirlpool model WDT910SAYM3 with power scour.