Sporadic fail of connection to windows share when using NTLM security

Issue

• Sometimes a previously working connection to a CIFS share is lost
• The ls output shows ? instead of showing the appropriate rights of the directory:

# ls /mnt
ls: cannot access /mnt: Permission denied
# ls -l /
...
d??????????  ? ?     ?        ?            ? mnt
...

• The mount is done using NTLM security e.g. as follows

//server/mount      /mnt/     cifs    nosuid,credentials=/etc/smbmounts/creds,uid=999,sec=ntlmsspi,gid=999,file_mode=0664,dir_mode=0775    0 0

• Unmounting and remounting the share does solve the problem.