A spotlight may work the initial time before you leave the settlement however, when you come back, they are nearly never working(showing effect of light.) A quick and very temporary fix is to re-attach the wire, however when you leave and come back it will be bugged again. This is unfortunate because spotlights give off the most light by far and are a nice little novelty to spread around your settlements. Definitely the most interesting light aside from maybe the mirror ball which is by the way also bugged in the same fashion.

Looking forward to a fix.