Xerox C315 scan problem on glass

[Jin Gitaxias]

Hello,

I'm having a problem with scanning. The scanner itself works fine when a single piece of paper is put on the glass, however if I put even a 20 pages thick book, an error occurs saying "An unkown error occured".

I've tried even using NAPS2, thinking it's a Xerox scanning software problem, however it doesn't work as well. Altough NAPS2 say that nothing is in the feeder for some reason even though I select specifically that I'm scanning from glass.