650d problem - buttons behaving randomly and shutter will not release

Hello,

I have a 650d that has been exhibiting odd behaviour. This happened before but stopped for a few months where it then worked perfectly, and now the problem has returned and is permanent.

When operating the camera with both viewfinder and Liveview, pressing the shutter to engage autofocus works correctly, but a further push of the button will not release the shutter (I have tried manual focus and all other settings - the same problem), however whenever the mode dial is moved the shutter will then open (and either remain open indefinitely, or take a correctly exposed shot which is saved to SD. If the the camera is turned off, the shutter will also release. Each click of the mode dial will then take a random picture.

The settings button all over the camera will at times do nothing, but at other times will work correctly, or even bring up the wrong menu! The touchscreen will register a press (change colour), but not open the various settings either.

Enabling the touchscreen shutter release allows photographs to be taken, but this is not practical. At least it proves the camera is capable of taking a photograph.

I have tried several lenses, updated the firmware and tried all the resets I can think of. The camera has not been damaged, got damp or affected in any way that I know.

My thinking is that this is a broken or damaged motherboard, and the camera is a write-off, but I'd be very grateful to hear of any suggestions or anyone else with this problem.

Thank you everyone,

Mark