Brother VX 950 Foot Pedal Won't Work?

I own an old Brother VX950 and the foot pedal will and will not work. I opened it and the wires are well connected. There is a ceramic box inside that has a tunnel in the shape of a circle. Inside there are small black discs like a hundred of them, when I took them out to sand them (in case they were dirty) some broke. I still put everything back together, even the broken discs and when I tried the pedal, it will not work.

I pushed the the pedal plugged and open, when I pushed the copper plate against the top of the black discs, sometimes it will work, other times it won't. What are those black discs? Where can I find a substitute, a compression spring that fits that tunnel made of an electricity conductor? Or where can I get those discs?

By C. L. from Orem, UT