Hi wlee,
See if changing the name of the scan filename temporarily fixes it. The reason being that most Xerox machines by default keep adding a number to the end of the file. So the scan is called DOC.pdf then the numbering goes from DOC001.pdf - DOC999.pdf for example. The issue that comes up is it won't go past 999, so you will get these kind of errors in those cases, you don't even have to have all those files in there as it just checks the latest file, if it is there it will fail.
I have no idea about your device and can't find one on the Xerox LAN, but that is how most Xerox and FujiXerox controllers work, so at the device, if you change the filename and it works, just change the default filename to DOC1.pdf fo rexample and it will chug along just fine and keep the same schema as before and be totally transparent to the end-user.
Other stab in the dark guesses on the issue are as follows.
1. Somewhere there is a leading or trailing slash in the SMB repo setup, and since the device adds those itself, it will cause it to go like smb:\\192.168.1.1\scan\\docs\\dave, and since the device is UNIX, it thinks it should look for, or create a folder with no name
2. Server is on Windows 2012 and the MFP can't do SMB3 or can but is set to use port 139 instead of 445
3. Username for the printer is a domain account and entered as Domain\User instead of Username@Domain (This is a big one in Server 2012 when scanning from an MFP)