Ok, I have been looking on this community for similar problems and solutions.  Found it.  I uninstalled SupportAssist (only - the main one) and then came back online on this site to reinstall the latest version.  That took care of the update issue for now. For anyone who wanted to know.  However I ran a scan and came across another issue - saw this message:      "Hardware Scan Result (Manual) - Default scan - Exec Command Failed" Hopefully just a fluke and nothing is wrong with the hardware!    
Hope someone from Dell Support can help me. I have the EXACT same problem as Russ Elliot. Having an XPS 8930 that fails to install SA (SupportAssist) OS recovery tools v5.1.4.11989 since August.  Dell says it is an "urgent" update so I am concerned it fails to install.  Shouldn't have this problem with a 10 month old desktop. Please tell me exactly how to fix this error. My machine is only 10 months old. Thanks much in advance for your help.
XPS 8930, SA OS recovery tools v5.1.4.11989, fails