I dont normally use lighting in Rhino but Im setting up a scene that needs it and the lights are creating circle rings where the light lands. I have done a quick scene to demonstate and you can see the multiple rings in the background cube.
Thank you for taking an interest in this one. I managed to solve it. Basically the spotlight tip was aligned with the ceiling and the cone 200mm below. By moving the tip 0.01mm below the ceiling surface prevented the interference in the light beam.