Upload & Sell: On
I have an interesting situation with my five month old 6D. Here's how I described it in an email to CPS Canada.
I have a problem with my EOS 6D. It does a double exposure (at least, a double mirror flip) when it's turned off and when it's turned on. It says "Err 20 An error prevented shooting. Turn the camera off and on again or re-install the battery". I have done these things and it's still the same.
Aside from the double-clutch at power on and power off, it does nothing, except double-clutch when the shutter button is pushed (sometimes it double-clutches twice).
Also, if the camera is turned off and has no battery in it, it double-clutches when you close the battery door, after installing a battery - even when the camera is "off" at the power switch.
I found a couple of online references to Err 20 on the 6D, but nothing as exotic as a shutter double-clutch .
I'll let you know how it turns out...