Hey rosenkranz -
So there are a few things that could possibly be the issue here? If you are using LPVs, I would look at the emissive nature of your materials and see if the contributions by the emissive of surrounding materials may be leading to a hotspot in your level. This is pretty unlikely but worth mentioning. Do you have any particle systems in the level which are using emissive materials or lights in them but are on the other side of the wall that you describe in your narrow area? Particle Lights do not respect walls and will bleed through them. The actor which you refer, is a blueprint? Check to make sure that your lights are indeed Static in the blueprint, the default is stationary.
We have not heard back from you in a few days, I am marking this answer as correct for tracking purposes. If this issue has persisted please feel free to post additional information and we will continue to assist you.
Thank You -
Eric Ketchum