[TheThings5926]

Interesting, the conductive paint may help but I don't know how that will affect the encoders. I think if the encoders didn't have a plastic case you would't be having this problem so the paint might help. I think if you switch to AndyMark motors you wouldn't see this problem anymore. You could try wrapping bare wire around the encoder and connecting the bare wire to the frame. This will ground the encoder to the frame. Is the encoder actually hitting the ramp or the motor? If the encoder is hitting the ramp you could try a metal skid plate that is grounded to the frame too, this will take the shock and ground it into the frame and not your encoder.

Also, why do you use plastic printed motor mounts? For static isolation?

Best of luck!