I know it won't help you much now, but for others having this same thing done, here is how it should have been to keep the box from flexing.
That 2x4 could go on either the top or the bottom of the box. Sometimes, on a long box, we put it on both top and bottom. Creates a minor hassle for the electrician sometimes, but they know how to work around it.
That 2x4 could go on either the top or the bottom of the box. Sometimes, on a long box, we put it on both top and bottom. Creates a minor hassle for the electrician sometimes, but they know how to work around it.