Looks like Centrify adbindproxy is performing as expected, as a courtesy, I'm going to give you some tips.
If you're having a permissions issue, walk through the troubleshooting process:
a) Rule out user2's password as an issue
You can use this command to verify a user's password
$ adinfo -A -u user@example.com Active Directory password: Password for user "user@example.com" is correct
b) Rule out user2's status (perhaps testing you might have locked the account)
$ sudo adquery user -A user2 | grep account accountExpires:Never accountLocked:false accountDisabled:false
c) Rule out the group membership at the client level (Centrify)
$ sudo adquery group -A your-group | grep members members: [a list of users will show up here]
Note that the group would have to be UNIX-enabled too; not an issue for you since you're in Express/Auto Zone mode.
d) Rule out the filesystem permissions
$ ls -ald /path/to/your/filesystem/folder
You need to make sure that you granted the corresponding right to a user or unix group. Correlate with the results from the previous step (c).
e) Rule out the Samba Share permissions
Looks like you already have done that. This entails looking at the stanza for the share int he smb.conf configuration.