I have a Canon 7D Mk 1. Two actually. I bought one with an underwater housing, and it’s awesome. I bought another locally to use as a spare in case there’s a problem with the UW camera. Housings cost a lot more than cameras for most models, so it’s good insurance to have a spare camera.

Anyway, some time ago the 7D (land) model started to fail. I got “Err 20” errors when I’d try and take a photo. At first it seemed to correlate to using the pop-up flash, but later it simply happened any time, and eventually all the time.

I sent the camera to a Victoria camera shop that could fix Canons, as it was a lot cheaper than sending it back to Ontario – the only Authorized Canon Center in Canada.

It was diagnosed with the problem “stutter failure”. The quoted repair price was good, so I had them proceed. After just over a month, it came back “good as new”. Except, after a couple of weeks, the “Err 20” returned.

I sent it back under repair warranty, and the tech said “I don’t know”. So they sent it back to Canon Canada (in Ontario) to have it diagnosed. It turned out to be the mirror box, which was replaced. Fortunately, it was under repair warranty so I didn’t have to pay anything.

As it turns out, there is a very rare case where both the shutter and mirror box fail, but you can’t diagnose the mirror box until you clear (i.e. fix) the shutter problem. That was the case for my camera.

At any rate, it’s back now and working perfectly. I’ve been using it to take my renovation photos since it came back.