vertical lines in a Toshiba TV

[old_tv_nut]

Yes, it's possible this is a design flaw with this chassis, but it's so clearly visible in your photo, I wonder. I presume the bars don't move wildly, just get stronger or weaker when you change brightness?

You might try running added ground wires between boards, not following the path of the original ones, to see if it changes. (Still grasping at straws here.)