Caulk can be old cracked or even missing between the corner boards and between window edges and siding.
Roof leak water move around.
The drip is often.
Often wind driven rain comes in from above the roof especially around windows between corner boards and siding and through cracks and knotholes in siding.
Recaulk the corner flashing if any areas have hardened caulk.
Identifying the cause.
Move the light up the roof and away from any drips to find where the water enters the attic at the dormer.
A roof leak is always a cause for concern.
The water damage from a roof leak can extend well past the location of the leak.
The light reflects off the water as it enters the attic near the dormer.
Even if the roof leak is caused by a windstorm or a tree.
A standard homeowners insurance policy will cover water damage and roof leaks unless they re the result of gross negligence on your part.
Replace any missing or rotted siding above the step flashing on dormers.
Water doesn t always come in at the shingled surface.
Dormer walls provide lots of spots where water can dribble down and enter the roof.
Both are definitely problems but right now you have an even more urgent one because a leak near a light fixture is a serious electrical hazard.