Cause

The cable uses two or more N conductors.

Solution

Change the potential type on one of the duplicated conductors.
To do this, double-click on the cable source component and switch to the Symbol / function data tab in the Properties <...> dialog. Click [Logic]. In the Connection point logic dialog, assign the function connection point 2 under Potential type a new value (e.g.) "undefined".

Refresh the connections and then start a new check run.