Can't login to SEPM after adding a 2nd LDAP server

I wanted to configure my SEPM for two Windows domains. In addition I added a second LDAP server, imported some OU from the new domain and created new administrator accounts with LDAP authentication. After server restart it is neither possible to login with AD authentication even with a local administrator account to the SEPM.
Is this a known problem and is there a solution for this?

I'm using SEP 12.1.6 MP3 on Windows Server 2012 R2.