197 non starting

Hi everyone

Has anyone had issues with the earth strap causing non starting?

Changed the starter motor a month ago due to my 197 not starting..when you pressed the start button there was nothing..no clicking or anything..changed the starter motor and it seemed to cure it..a month later I’m back in the same boat.
The replacement starter was a used one ( false economy I know ) I’ve been told it could be a faulty earth strap to the gearbox..anyone had any similar issues? Is it easy to get too?