Hi Far North Eric,
CleanWipe is basically the very last resort if it's still persisting after some troubleshooting steps and especially on a Server.
Can you provide the SIS_Inst.log because the SEP_inst.log provides very basic information that sometimes can be enough but strictly in some very specific situations.
SIS_Inst.log gather more information during the installation process.
You'll find out in %\ProgramData\Symantec\Symantec Endpoint Protection\12.1.3001.165\Data\Install\Logs\
Kind regards,
A. Wesker