Comment 65 for bug 1728012

I have no idea what 'more-magic' xsane uses, as simple magic of root using scanimage isn't sufficient.

as your diff shows no success, only 'permission denied' the cause of the failure can't be identified ...

maybe a

'export SANE_DEBUG_DLL=128'

As user
'strace xsane 2>strace.user.log'

As root

'strace xsane -L 2>strace.root.log'

Finally

'diff strace.user.log strace.root.log'

could be of help. Don't know. But it's worth a try, unless better ideas arise.