I have a vertical black line running through the

Most likely the LCD panel has detached one or more of the lines that go from the control ICs to the actual LCD cells.

It usually happens due to heat emitted by the TV and the lamps behind it.

There is nothing you can do about that. Get used to it or consider selling it.

I was able to pull a trick once or twice by locating where it was and pressing it hard by putting a firm object between the frame and the LCD then fastening the frame...it's not a good or reliable way to go about it though. Takes a lot of time and carries high risk of causing additional damage.

No service technician that I know would engage in doing it. I am more of a hacker by heart and my main source of income is not tv repair, so I did attempt it a few times and was proud of the result in at least one of them...at least for a while :-)

But bottom line is it's not worth doing it.

Of course there's a minimal chance that the tcon (LCD controller) board is to blame. But from what you describe it's unlikely.