I've added a new domain user - who is a member of the "Remote Desktop Users" group, but they are unable to log in to a domain member.
The error in event viewer is
Account For Which Logon Failed: Security ID: NULL SID Account Name: firstname.lastname@example.org Account Domain:
Failure Information: Failure Reason: Domain sid inconsistent. Status: 0xc000006d Sub Status: 0xc000019b
The client just gets "credentials did not work"