Did you at least check?
Because the image with the mapping off still clearly shows that the light on the left wall is not quite as strong.
Turning off the mapping, thus changing the appearance of the material/object will definitely give different lighting conditions, so I don't 100% believe that your hunch is correct.
Or, simply try just delete the lights and make new ones.
Or, check your bump mapping, is the bump somehow creating the effect?
Or, is one of the lights slightly rotated?
There are many potential causes, I would say this isn't a bug but rather something within the scene has gone wrong which only you can fix.
Good luck, mate.