Invisible dead body, not removable dead body in an power room causes the asigned dwellers to lose health fast. An empty room causes other problems. The room can't be removed becuse it is joined to two other rooms. The "haunted" powerroom is the smallest but fully upgraded kind. Two dwellers can be asigned to it.
I made three screenshot from different angles.
I tried to overcome the "haunted"-bug by letting a dweller die in the "haunted" by fire. And then remove the body. But that did not slove the issue.
Best wishes from the Netherlands