Description of Problem: When one is using ADF (automatic document feeder) and multiple pages to scan then xsane attempts to stick them into a single file; i.e. there is no provision to use --batch flag, possibly with a format specification, in an underlying 'scanimage'.
You need to pick a filename like 'image-001.pnm' and set 'Step' non-zero. Are you doing that?
Actually it turns out that putting a name like 'output-0', or 'ouput-1', and picking up an extension from a menu, will also do and a counter will be expandend automatically to its width which you can set somewhere else, but this was not really obvious to find. Moreover when you are using a feeder it is not enough to pick up ADF as your source but one has also set "modus" in "Enhancements" to ADF (default is "none") or pile of pages will be not scanned without a manual intervention. End of batch scanning is signalled on a screen with a pop-up alert which annouces "I/O Error". Technically correct as there seems to be only one exceptional condition and this is "I/O Error", even you just run out of pages to scan, but scares pants off with "uninitiated". Sigh!
I never claimed it was easy to use.. Closing.