Error in LdapGroupProvider

Hello.
I’m getting errors about every 15-20 minutes:
"org.jivesoftware.openfire.ldap.LdapGroupProvider - Groupname i7o33osvi5tecn42ndicol72dd9ca20f1o6 not found. " Ther’s no such group in AD. Moreover, it never existed.
org.jivesoftware.openfire.ldap.LdapGroupProvider - Could not find user in LDAP serveralert
Ther’s no such user in AD. Moreover, it never existed.
sometimes errors like org.jivesoftware.openfire.ldap.LdapGroupProvider - Could not find user in LDAP [real existing username], go. No complains from user.
Users are authenticated via LDAP. Looks like authentication is ok (users can log in, are distributed in groups correctly).
OF version 4.4.1. Installed plugins: Packet Filter(3.3.0); Search (1.7.2); Monitoring Service(1.8.0 ); MotD(1.2.2)
What should I look precicely at?
PS: error log increases about 1MB per day, that’s disturbing.