LDAP group mapping defined in XWikiPreferences is not working

I tried to set LDAP group mapping through the WebPreferences settings but it is not working. My xwiki.cfg file contains group mapping which is working fine

Here are my comments from XWIKI-2185 issue:
I added [XWiki.testGroup=CN=testers,OU=Groups,DC=company,DC=com] text into Ldap groups mapping field. Then I created that user's group in the xwiki. I am sure, user exists in LDAP group, but he is not assigned into the testGroup after login. LDAP groups sync mode is set to always, Update user from LDAP is set to YES. I also use xwiki.cfg file for group mapping. Group mapping in xwiki.cfg file works correct.

The user exists in XWiki.XWikiAllGroup.
I am using com.xpn.xwiki.ldap.authentication.XWikiLDAPAuthServiceImpl authenticator
There are no errors in log file.

My log file contains this:

DEBUG LDAP.XWikiLDAPAuthServiceImpl - The user belongs to following XWiki groups:
<here is the list of the goups, also XWiki.XWikiAllGroup is here>
..
...
..
DEBUG LDAP.XWikiLDAPAuthServiceImpl - All defined XWiki groups:
<here is the list of all defined groups together with groups, which are used in group_mapping configered using xwiki web interface>