BP_Lightbeam mobility?

I added a BP_LightBeam to my scene and associated it with my main Directional Light Source.
When I change the light source direction the lightbeam angle changes as expected, but only within the editor.

If I update the light source during PIE (light source is ‘movable’) then BP_LightBeam does not move.

If I (dynamically ) try to update the rotation of BP_LightBeam in an event graph I get this message:

“Warning Mobility of BP_LightBeam_5220 : StaticMeshComponent_6 has to be ‘Movable’ if you’d like to move.”

However, there is no option to set the BP_LightBeam:billboard to ‘movable’.

How can I resolve this?

Fyi, BP_LightBeam can be found in the BlueprintExamples demo.