I’m currently in the middle of the building escape part of the course, and after building my BSP brushes to make my room, I get this strange lighting bug:
I’ve googled it and can’t really figure out what the problem is exactly.
Are you talking about the black bars at the bottom of the back and right walls?
Are they BSP or a static mesh?
Yeah, they are BSP right now.
And if you convert them to static mesh and rebuild the lighting?
When I tried it on one wall, it just turned black, materials now don’t work on it and I can just walk straight through it.
Could you send your project to me? You can use File > Package Project > Zip Up Project and then upload that somewhere like Google Drive or DropBox.
I have the same problem here 
Is there anything known yet what the cause might be?