This is caused by DarkLights and the way doors are treated in FPSC. FPSC renders through doors just as it does through windows. Because it renders what's on the other side of the door even when closed, light travels through or is visible as well.
It will take some play to get the lights adjusted and positioned properly to work well, and the more walls you can place between the doors and lights the better off you will be concerning this and framerate as well.
Best.
I'm sorry, my answers are limited. You must ask the right question.