For "CASE 1" above, I modified the scanimage commands to reduce the file size, eg:
"scanimage --mode Gray --resolution 200 --compression JPEG --format=jpg > abc.jpg"
And the scan works.
Therefore, I am now confident that this is a file size issue. For large files sizes above roughly 10MB, I get the error "Error during device I/O".
UPDATE:
For "CASE 1" above, I modified the scanimage commands to reduce the file size, eg:
"scanimage --mode Gray --resolution 200 --compression JPEG --format=jpg > abc.jpg"
And the scan works.
Therefore, I am now confident that this is a file size issue. For large files sizes above roughly 10MB, I get the error "Error during device I/O".