This is a story about my own 7d, which has been flooded with water, before I have purcesed it “as it is”, practically not working. I repaired it in a few hours -worked well after.
After a certain time stopped working, message was Exposure not possible, ERR20. Mirror moved up, but the curtain not. Other lots of hours of repair, disassembly-assembly. Normally I should change the shutter, but is really expensive. So i have rathr bought the SPT software for the 7d.
I have read out tge fault memory. And it was a problem regarding – the mirror motor position.!!!
Disassembled again – no sign of anything unusual.
Assembly – works. Second day in the morning – NOT working.
I resoldered MANY times a damaged cable sochet, which was not so easy, as the former corrosion has damaged the contact surfaces.
Then I realized, that toutching the motor, the camera workes. Pushing it in another direction, the fault appeared immediately. Wow. The motor here is fixed to it’s frame only through 2 flexible points – 2 screws and two rubber collars. I dieassembled a 99% similar motor from an old 40d – this has no flex joint, just two screws. No problem – I had no other solution anyway. So, i made both operations (out and in). And even after 3 days the camera is working perfect.
So, never give up!