Bootleg neutral or some other alternative path would be what I would look for.
Originally Posted by hnieves85
With a MWBC if you loose the neutral the lights could, possibly work through both legs of the 480V. Its possible that the lights don't blow up because even though it's a 480V circuit all the lights would be in series between your two hots. Not an possibility I would consider in this situation.
Once in a while you get shown the light
In the strangest of places if you look at it right. Robert Hunter