It's not so much of a bug as it is shoddy workmanship. Light sources look they were arranged improperly.
Newsflash: This was present in Oblivion, Fallout 3, and New Vegas. Don't forget that everything in the game was placed there manually.
By the way you describe shoddy workmanship I suppose that means that you can do better than the Devs. did? hey if you can do better, go and apply for a job at Bethesda or Obsidian, maybe then you can single handedly straighten it out, I'd be ever so grateful if you did.
Sorry, but the reason I posted that link was for OP to post his problem in the Bugs thread as previously mentioned, I only provided the link since he/she couldn't find it.