Hello,
I have seen this in the past and from the way you are describing it I think possibly the same thing is occurring here.

If the eu domain is a child of the main server that is entered into the LDAP domain URL it will automatically attempt to connect to the children. If what I just wrote is correct, the issue lies in that the authenticated user for parsing the LDAP system is designed to have permission and be able to parse everything from the parent domain and also parse everything below (to include all children that are nested below said parent domain). In this case the eu domain being not authorized to allow this user account, it is then throwing an error each time it is attempting to parse and connect to that child domain. Unfortunately this is the design of how things are handled within the LDAP system and they can't be changed (other than removing the child to another forest outside of that domain, giving it authentication permissions, or choosing a different child domain to authenticate into that wouldn't have hierarchy with the eu domain) as this is the nature of how the LDAP parsing occurs and is not a specific functionality of ALM (as ALM is basically a conduit to LDAP and nothing more).

I am suspecting that this is the case and other than mentioned above resolutions the errors will continue to be generated but the good news is that they are affecting nothing and only a nuisance in the log file.

Hope this helps,
Dan