If restarting the spooler on the server fixes the issue, the server is the problem. Easiest fix is to remove any un-necessary stumbling blocks. So those 2 things that will make no difference to anyone would be the SNMP option in the port and the Advanced Printing features option (You lose nothing by disabling it)
On the Server go into the Printer Properties > Ports > Configure Port and uncheck the 2 boxes at bottom and click OK
Then go to the Advanced tab and disable the Enable Advanced printing features option
And after that, while it likely won't fix anything, update to the latest spar firmware here,
If that doesn't fix it you have serious issues and would have to call Xerox, and likely pay to have an analyst diagnose the issue via Wireshark Trace and capture to see if the Xerox plays any part in the issue. You can do that yourself if you know how but it is way too involved for me to document here.
