As I posted earlier, my Canon 5DMkIII was having dust/dirt building up in the viewfinder after I sent the camera off to have a battery draining problem fixed, because of Canon Repair fixing a ‘light leak’ problem, that I had nary an issue with.
I sent Canon an email, and one of their reps called me, and told me they would review the problem and my comments, which I took to mean “Suck it up, we’re going to charge you some more.”
I was wrong. Both the focus screen and prism have been replaced, and I haven’t been billed for it. I guess I was right as to how the dust was finding it’s way in.