Ok, but the wires and contollerboard were covered by metal the whole time? Are there any cables on the back (flat ones?) that run in the breze?
You mean the whole monitor, e.g. you doublesided the stand to the back?
As the lines are pritty evenly propagated over the screen I still think its a connection error, as most likely one contact delivering the signal to the LCD is not good. (get better with heat worse with cold.)
Are there any naked circuit boards or cables on the back? (picture of the backside maybe?)
Try to kinda not "hang" the screen on the stand.. cut the doubleside and lay it flat down.. maybe the fact that you mount the stand onto the metal backing causes strain, were it not should and that loosens the contact.