Error on some Agents shows 'Agent Registration failed' while actually they were registered with the NS and Site server properly.
Sending basic inventory and receiving update configuration is also working fine as far as you can tell.
Verified that the affected client machine is not on multiple Targeted Agent Settings policies:
The machine-default permission settings do not grant Local Activation permission for the COM Server application with CLSID
{C2F03A33-21F5-47FA-B4BB-156362A2F239}
and APPID
{316CDED5-E4AE-4B15-9113-7055D84DCC97}
to the user EXAMPLE\AltirisAdmin SID (S-1-5-21-1957994488-2139871995-725345543-1261163) from address LocalHost (Using LRPC) running in the application container Microsoft.Windows.ShellExperienceHost_10.0.19041.1023_neutral_neutral_cw5n1h2txyewy SID (S-1-15-2-155514346-2573954481-755741238-1654018636-1233331829-3075935687-2861478708). This security permission can be modified using the Component Services administrative tool.
ITMS 8.x
Make sure computer is targeted only by one Targeted Agent Settings Policy (under Settings\All Settings\Agents/Plug-ins\Symantec Management Agent\Settings\Targeted Agent Settings)
If applicable, remove it from the target of the second policy.
Based on warnings in event viewer:
Reboot the Computer