bit of a follow up as someone liked my comment above today..

noticed a strange noise & thought it was a timing belt idler pulley, ripped the belt cover off & found gouges on the back of the belt, ripped it further apart to find the belt looking like this:



seems when the 100,000km service was done (using a gates belt) the guide over crank pulley was installed hard against the belt resulting in melting the belt & delamination

moral of the story... don't get [insert generic non-subaru specialist workshop name] to do your timing belt service

so lucky, could have ended in tears & new engine time