Sorry I don't know electronic components for the boards well at all but hopefully one of our knowledgeable members will be along soon.

One thought is if the lights above the stop buttons don't light up then the spin knob could be problematic. I know for stop buttons that light up themselves normally, will not light up if the spin knob is held down or stuck. I wonder if the lights are to come on once the spin knob is released? Going with this thought it may then be worth pulling the spin knob for inspection.

I will also check my storage in a day or so as I may have a few spare stop boards left.