It is a formal raising of an issue with Xerox for problem resolution. I believe it stands for Software Problem Action Report.
There are no pre-flight performance problems known within the 5.1.0.x releases. You could upgrade to the latest release 126.96.36.199. You could also contact Xerox support to look into the problem.
The SW level can be obtained by selecting the "About" selection on the bottom on the GUI display. Within the blue splash screen a Version number is displayed (e.g., 188.8.131.52).