How are you getting a reference to the actual actor in the level?
Typically you’d do Get all actors of class (Sunlight_Blueprint) → Get copy (0) → cast → Set Light Ref.
Furthermore you do the cast and set reference (light Ref) once using the Begin Play event. Then on Tick (every frame) use the reference variable to modify the light…
Just as an FYI you shouldn’t be hitting the directional light on Tick. Unless you are modifying it every single frame.
e.g. 60Fps would mean 60 modifications per second on that light.