Hi,
Error code "5" means access denied, even though you are running a supported version of Symantec Data Loss Prevention (DLP) it does not mean that it might not interfere with your Windows 10 upgrades, as it has already done so in the past.
It could be that the Symantec DLP may be locking the registry during the first attempt, in your case I would be in touch with Symantec to see if they are aware of this issue for upgrading Windows 10, version 1809 -> 1909.
https://community.broadcom.com/symantecenterprise/communities/community-home/digestviewer?communitykey=65cf8c43-bb97-4e96-ae0b-0db8ba1b4d07&tab=digestviewer
Otherwise you could simply perform the resolution that was provided in the KB article for upgrading from Windows 10, 1709 -> 1809:
https://knowledge.broadcom.com/external/article/184753/upgrading-windows-from-1709-to-1809-fail.html
Best regards,
Leon