It's entirely possible that the fault is actually as you've suggested.
I'd try degaussing the middle of the line, in the hopes of shaking
the wire loose.

Get a rubber mallet and hit it in the face - pretty hard. If the
aperture grill lines are twisted, that will set them straight. I've
done this after a nasty trip with an external degaussing coil.

Simply lifting the set and dropping it gently (???) might fix the problem.
This happend to my Sony WEGA in March when it was moved from the LR to the
BR. The splotch disappeared, and has not come back.