Hello.
I am using the same scanner for a long time : EPSON PERFECTION V500 PHOTO.
I can't say from when I it is not working as expected.

Both last and previous software version run into the same problem.
Changing Epson driver to old avasys driver is without help.

Presently, after returning to previous version by deleting the driver, and deleting xsane, and then reinstalling previous driver and previous xsane :
Code:
user_test@linux:~> rpm -qa | grep iscan
iscan-data-1.14.0-1.noarch
iscan-2.28.1-3.x86_64
iscan-plugin-gt-x770-2.1.2-1.x86_64

user_test@linux:~> rpm -qa | grep sane
xsane-0.998-8.1.2.x86_64
user_test@linux:~>
For the following I can't say if it belongs to that previous version.

sane-backends-autoconfig-1.0.22-22.1.4.x86_64
sane-backends-1.0.22-22.1.4.x86_64
hplip-sane-3.12.4-3.1.2.x86_64
libksane0-4.8.5-2.4.1.x86_64
With the three kind of driver :
If I scan a document, and ask for b/w document, the generated pdf file is OK.
If I scan a document, and ask for color document, the generated pdf file is OK.
If I scan a document, and ask for gray scaled document, the generated pdf file is bad ( duplicate image in one ), but the document showed in the viewer is OK.

Help is welcome.