Spotlight causing flicker

My camera is inside a cockpit, which is covered in a translucent glass texture, which is a bit dirty and reflective. Outside the cockpit I have a large spotlight. The glass texture is somehow being illuminated by the spot (whose cone does not intersect the glass), and when I move the vehicle this illumination flickers, depending on how fast I move. If I stand still, the illumination is constant. If i start to move very slowly, it fades in and out, and if i move quickly, this becomes a really annoying and irregular flickering. The indirect lighting for the spot is set to 0. Any suggestions as to what might be happening here?

I replaced the spot with a point. No difference. Any suggestions? Is light bouncing up from the landscape?

The only solution I got working was to add the light to a different channel so it didn’t effect the windows only the interior of the cockpit.