[Samba] Point'n'Print problems

[Lars Hanke]

I followed the tutorial at 
https://wiki.samba.org/index.php/Configuring_Point%27n%27Print_automatic_printer_driver_deployment#Uploading_printer_drivers_for_Point.27n.27Print_driver_installation 
to centrally store printer drivers on the print server. However, when I 
try to "Add Driver ..." I get an error: "Access denied."

The account has SePrintOperatorPrivilege

root at samba:/# net rpc rights list accounts AD\\mgr -UAdministrator
Enter Administrator's password:
SePrintOperatorPrivilege

I created a print$ share:

[print$]
         path = /srv/samba/Printer_drivers
         comment = Printer Drivers
         guest ok = no
         browsable = yes
         read only = yes
         directory mask = 0775
         create mask = 0664
         write list = mgr,Administrator

The POSIX permissions for /srv/samba/Printer_drivers are set that mgr 
should be allowed to write.

What am I doing wrong?

Thanks for your help,
  - lars.