Cause

Identical designations were entered for a PLC box containing bus data in the Rack ID and PLC card is placed on rack ID fields, which means that the rack is mounted on itself.

This check run only checks PLC boxes at which a configuration project is entered.

Solution

Open the Properties <...> dialog for the corresponding PLC box. In the PLC box tab, enter different values into the Rack ID and PLC card is placed on rack ID fields.

Then start a new check run.