I just replaced mine for a similar reason. The metal pin should have a rubber bushing on both ends, and the pin/bushing should be approximately in the center of the slot. As the mount wears, the rubber becomes compressed, which lets the pin rest on the bottom of the slot, rather than in the middle. At least, that's what happened to mine. When the pin is resting on the bottom of the slot, you basically have metal to metal contact, with no capacity to absorb vibrations.
Hope this helps.
