Thank you for the hint Senz.
From a logical point of view, the Default Lead Selection should not have a significant influence on my problem as the same behaviour could be triggered by manually selecting a line item.
Anyhow, this is interesting, because when switching Default Lead Selection to "true" on all subnode-related data lists, the following happens:
When I open an existing BO instance, items in the subnode "Results Per Employee" show up for a fraction of a second and then they disappear.
>> It seems that the "sub-items-retrieval/query" somehow doesn't work correctly in this case.
Kind Regards
Pablo