| I would go through and reseat all of the connections between the PH and PWB-A. Visually check for pinched wires along the same wire bundle/ribbon. I think there is a ribbon cable in there.....carefully clean the contacts on the ribbon cable with a soft pencil eraser.
Otherwise, you need to narrow down the problem between the PH or PWB. BTW, even though the poly motor is turning, speed could be off, the SOS sensor is bad, laser is dead, etc. | 
Linear Mode
