Thank you so much! A strange hack but it worked a charm :)
I actually had some trouble with this because the room, after shooting a switch, needs to go dark and have the lights start blinking. As it was, changing the brightness level by 1 left those particular sectors almost fully illuminated against the darkened sectors. Thankfully, thanks to some further voodoo doll trickery (start lights blinking; then set brightness to 35), I got the effect working just fine and the renderer issue is absent.
Thanks again!