[paulsherwin]

The contacts are dual sided and riveted onto the paxolin base. The idea is that they grip the sliding bits of metal on the upper bit of paxolin on both sides. This was never a good arrangement even when new, and over time the contacts have been bent and distorted by the sliding bits of metal failing to engage properly (the tolerances are very loose). They have also suffered some stiffening and metal fatigue.

As I said at the start of the thread, the contacts are probably repairable, but not by someone with my level of metalworking expertise.