Hi
if you have a look at the agent log it shows chick privilege is missing:
20181205/195506.129 - U02001040 Error in function 'CreateProcessAsUser', error code '1314', error description: 'Dem Client fehlt ein erforderliches Recht.'. (sry for the german message, its a german OS)
If you do not read or write from C:\Windows then it needs no access rights.
The builtin admin account is sometimes a bit tricky to configure correctly, I usually use a local user with correct privilegues.
Another hint is UAC - turn it off for testing purposes.
cheers, Wolfgang