Welcome to the Centrify Express forums.
Always confirm the version of Centrify being used and the platform when posting. E.g. CentOS 7.3 with Centrify 5.3.1
Although there are different potential issues here, first I'd make sure that:
a) The samba server is using the latest version of Centrify Express
b) The samba server is using a unified identity scheme with the Centrify IDMapping Module for Samba (adbindproxy).
(can be obtained from the Express download site)
Ultimately the Samba Server needs to know who the user is regardless of the permissions of the share/printer. If you're using winbind as the identity mapper, the range may be from 1000 to -20K (like your config file below), but there's no way for the server to do a correct mapping for UNIX identity (login, UID, Primary Group, GECOS, Home, Shell). Centrify Express emulates this locally on the box, but without a mapper that unifies the Identity generated by Centrify express, Samba will use the predefined rules on the config file which could cause the prompt.
I would start with that, and continue troubleshoting.
R.P