E000840 (shutter error)
0001 Indicates that the HP sensor signal is not detected when the shutter is operating, after executing 3 retry operations.
0002 The interval of ON-OFF detection by the sensor in response to shutter operation is shorter than a specific time period.
The shutter is set to the appropriate position by driving the shutter motor (stepping motor) for a specific number of steps. A cut-off is found in the periphery
of the shutter gear (front) operating in conjunction with the shutter; the machine checks to see if the shutter is set to the appropriate position with reference
to the output of the shutter HP sensor (PS53), i.e., whether the sensor has detected the cut-off.