If you mount or access a CIFS share using the local user without netbios or cluster name, the operation fails

There is a behavior change in the latest SAMBA version. SAMBA checks for the domain name passed by the client while mounting the share. So if local users access or mount a CIFS share, the netbios name or cluster name along with user name, <netbios_name>\<username> is required. The netbios name cannot be empty.

(IA-31907)

Workaround:

Mount (or remount if you have upgraded from SAMBA 4.6.11) the CIFS share using the cluster name or netbios name.