And as for cosmic rays...this may be a sensitive topic for you (or maybe you're just in a condescending mood), so I'll tread carefully, but seems simple to me.
The actual cause of the problem, given the instrumentation in place at the time of incident, is unknowable. But it might have been a subatomic particle. It absolutely definitively is, sometimes.
Metonymy might be imprecise, but it's human. I'm not sure what standard you intend to hold commenters here (or old guys with computers) to.
Cosmic ray is the appropriate colloquial term. Just like "bug" is the appropriate term to describe computer problems that have nothing to do with insects. It's a well established colloquialism and not simply terminology made up on the spot like in your example.