How do I fix this?

I have a used PDP CX kit and last weekend, when I tried to disengage the throw off mechanism on my snare drum, a screw or something else fell off (maybe inside the mechanism -- I can hear a metallic part moving freely inside of it) so that I cannot reset the tension of the snares anymore. You can see the missing screw in the pics below. Does anyone have an idea how I can fix this? What am I missing? What size of screw/nut/washer do I need? Should I replace the whole mechanism? I contacted DW Customer Service, and they asked for pictures. So I sent them the ones below. I'm still waiting for a reply. In the meantime, I was thinking that maybe someone on here experienced something similar and already found a cure? Please help me.

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How do I fix this?