I'm willing to bet it isn't up to date, My guess is you are on the General Release that would be 73.040.075.34540 which had that issue also on Server 2012. But if I am wrong here, feel free to have the printer do a wireshark trace and do 2 scans, one that works and one that doesn't, then stop the trace, save it, and PM me a place I can retrieve it to review.
But if you are not on the current as of today 073.040.237.28600 release, update first or you won't have the network trace ability or the fix for the known issue it appears you are having.
Had the same problem storing multipage scans on a Synology NAS. Updating the Xerox printer to a newer version fixed it.