Join into an existing MS AD Domain failed

I want to setup a UCS-Domain and sync it with an existing MS AD-Domain.

During the installation of the first UCS-Server I chose the option ‘Join into an existing Microsoft Active Directory domain’
After the installation process some errors/warning occurred.
I decided to go on and to deal with the problem later.

Now i have discovered that one join-script did not succeed.
When i rerun the join-script i get this error:

root@ucs-master:~# univention-run-join-scripts --ask-pass
univention-run-join-scripts: runs all join scripts existing on local computer.
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Enter DC Master Account : myaduser
Enter DC Master Password:

Search LDAP binddn: Permission denied (publickey,gssapi-keyex,gssapi-with-mic,keyboard-interactive).
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,keyboard-interactive).
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,keyboard-interactive).

  • Running join scripts failed! *

  • Message: binddn for user myaduser not found

myaduser is a MS AD-User with admin permissions.
Its DN is
CN=My ADUser,OU=Location1,OU=AD-Accounts,DC=sub,DC=example,DC=org
Maybe this uncommon DN is the problem?

Any help is welcome
Thank you

UCS version is 4.4-5 errata686