Cannot manage why polyline primitives rotate/flip on mouse move, what's going on?

Dear Community,
Goal: define multiple polyline instances and add them to primitive.
Issue I am facing: Cannot get my head around the polyline that are plotted on the map but are weirdly rotating or flipping on mouse move. What’s going on?

Sandcastle cesium example polyline primitive

Appreciate if you could help me, thank you in advance!