DMX BP_MovingHead Dimmer doesn't work with Volumetric fog

My DMX setup works fine except when I use ExponentialHeightFog and turn on volumetric fog, the light is still visible even if I set the dimmer value to be 0.

I can see the realtime change of Light Color of the spotlight component which is part of the BP_MovingHead when I run the game, but the Intensity won’t change with the dimmer value.