Answer to "Camera gets Err 30 message. How do I fix it?"I also have the same problem with my 5d mark iii error 30 keeps popping out even if I replace the battery. So I removed the lens and raised the camera mirror up, I found that the sensor cover was squeezed. I straightened it. Buh the upper one is not as tight as it was. So every 3-4 clicks then error pops out again..