Very recently one of my cameras develops a problem with a component "A".
A consequential failure which impaired the camera to the point of rendering it almost inoperative.
Sent it to Canon to repair under warranty. After about 6 weeks the camera is returned with the following work report: " Component "B" replaced, camera cleaned and checked OK."Now that didn't sound good off the bat. I never had a problem with the component "B", and there is no mention of defective component "A". Well, heck, what do I know....after all, they are the experts. Turned the camera on, tested the function of the component "A", and sure enough, the same old problem is still present.
The camera goes back to Canon. I restate the problem and highlight the fact this is a repeat service request for the very same failure as before.
Now this gets interesting. Within three weeks the camera comes back with the following work report: " The camera checked and it operates according to Canon specifications. It is suggested that the customer checks his lens for a source of problem". Now, I have just about resigned myself to having to follow their "standard" procedure which says that it takes them three attempts before they might get things right.
However, just for the hell of it I checked the component "A" again. Whaddaya know, it works perfect now. Hmm......so what gives ? Has the camera fixed itself in shipment ? Have I lost my mind ? Not bloody likely.
Hehe this happened to me when I had a 1d Mark III. The unit didnt turn on and I sent it in and they returned the next day and it worked, with the same message as yours.
I would bet that they have sheepishly repaired part 'A' without telling you so they dont have to admit their incompetance.
God if you had to check it with your lenses the thing would be out of warranty by the time you finished doing all of them
The line I liked, after repeated complaints, was "we have been able to verify the issue, the fault is intermittent and as such could not initially be diagnosed." Intermittent in that it failed only when I used it?
Turned the camera on, tested the function of the component "A", and sure enough, the same old problem is still present.
Hmm......so what gives ? Has the camera fixed itself in shipment ? Have I lost my mind ? Not bloody likely. 
