hi seamus,
mine vibrated going over small bumps on the road, mine is a petrol engine, so its very quiet when idle. but im attaching the damaged and undamaged mounts so you can see the difference

i have stuck a small piece of rubber in the damaged one to eliminate the vibration temporarily until i get the exhaust mount removal pliers from ebay. (i dont like to stick a screwdriver and pry)

compare it with the undamaged one.

Attached Images