When a user clicks the center button on the separate navigation control (the standard buttons are collapsed) then a line appears at the center-bottom position.

Reason for closing/ declining:

The separate MapNavigationControl is designed to be used outside RadMap.

The bug is only reproducible when the control is placed in the ItemsCollection of the RadMap which is not supported. 

Bing map provider does not work over HTTPS due to the fact that the tile images of Bing currently use different URLs for HTTP and HTTPS.