In the first two screenshots, you need the wall to go slightly past the floor level. The lower the better. If it’s intersecting perfectly with the floor, it’s not good. It needs to go lower than it.
In the second set of screenshots, I think you need to also extend the wall that’s perpendicular to wall that’s displaying the light bleed (looking at the last screenshot). It needs to push into the other wall quite a bit, or you could just break the wall that’s displaying the bleed into two sections instead of one, to isolate them better.