All you have to do is to set directions as a single Vector3 which is the direction which the lines should face to and set the directionsAutoMode to:
ribbonOptions: {
directions: BABYLON.Vector3.UpReadOnly,
directionsAutoMode: BABYLON.GreasedLineRibbonAutoDirectionMode.AUTO_DIRECTIONS_FACE_TO
}
and you don’t have to set directions for each line to different values separately.
@phill2mj please mark this answer as Solution