When dynamic lights are placed (the kind of lights that, for example, turn on and off depending on whether it's day or night), we have the decision of whether or not the light casts shadows. If shadow casting is off, things like this happen. It looks like that is probably what is happening here. The problem with shadow casting is that it comes with a performance cost. Also, due to engine limitations, having too many shadow casting dynamic lights nearby each other is not allowed. It's a combination of these two reasons that explain why many lights in the game behave this way.