As I wrote in this thread a long time ago, this issue is not common in the USA (whose engine population is some 10x bigger) and appears to be due to "something" peculiar to UK engine rebuilding practices.
I'm not sure I agree.
There have been problems outside of the UK and with rebuild shops that have many years experience. The problem started all of a sudden, I suspect there was a change in spec for the plugs or some related part which precipitated the problem.
Lycoming outsourced a lot of their parts manufacturing and as a result lost direct control of the QA process. Remember the issues with the crankshafts a while back.