Spanner juggler is bang on with his advice, as always.
In addition, I would always plop a vacuum cleaner hose over the plug recess prior to removal, to suck up any loose
debris that may fall into the cylinder.
Recommended torque is 10 to 20 Nm, which ain’t a lot!
Removal at least once a year should reduce the issue. Due to the longevity of plug electrodes, I am not convinced that all dealers do this on an annual service! ( despite what you pay them!)
