The Xerox devices are configured with high security enabled by default.
One of these features is Immediate Job Overwrite.
From time to time and for any number of reasons, this feature doesn't work for certain jobs.
Here is a Xerox KB article on how to Perform an On Demand Overwrite Using CentreWare Internet Services (CWIS).
Here is a Xerox KB article on how to Perform a Disk Overwrite From the Control Panel
If this issue occurs regularly, you may wish to disable the feature altogether - use these instructions but disable it instead.
However, to obtain a happy medium between security and functionality, you may wish to enable the scheduled image overwrite and have the action perform overnight. This action will actually remove any error messages on the device so should you decide to leave the Immediate Image Overwrite enabled, the schedule Overwrite will remove any errors that occur when a job cannot be removed.
With the above set, it will perform an automatic reboot which causes the configuration sheet to be printed. Therefore, you may wish to disable the configuration page at boot up...