I know nothing about this particular issue (indeed, I'm only about 80% sure I'd recognise an Enstron 480), however...
A few years ago, working for an organisation supporting a fixed wing aeroplane, I had cracking in a critical component (a wing attachment) reported to me from the field. I did a fleetwide survey and discovered that it actually occurred on a reasonable proportion of the fleet and the component had fairly routinely been replaced WITHOUT anybody reporting a trend.
CAA, looking over my shoulder said "you need to ground all of those", I fought back saying that was totally unnecessary for, maybe half a day until I came to my senses. I agreed to a grounding and modification and I'm pretty convinced that if I hadn't, we'd have had a fatal by now.
But, the owners hated it - I lost track of the number of times I had to defend that decision, either in public or private. My organisation and the CAA came under an enormous amount of flack and, yes, there had never been an in-flight failure.
Yet!
So, knowing CAA's competences and approach, plus what we'd all say if there was a failure next week and CAA hadn't done anything about it, I'm afraid that I feel you're being a bit unfair here.
That said, as an organisation, they are lousy at communicating with the public. So your "where's the evidence" criticism is almost certainly valid. I'm sure that they have it, but should also put it on the table for everybody else to have a look if they're costing operators that much time and money.
G