I have one vertical dotted 1px thin vertical line on my LG 55SM86 tv. I opened and checked every ribbon cable and it did not fix it. What is reason usually for this kind of thin line? Could it really be cable fault or 100% its within led panel itself as its not “band” that is faulty but just single line? Is it safe to swap left side cable ribbon with right just to check if its cable fault? Asking as on cable there is warnings written LEFT! and RIGHT! side, or its just for factory workers and repair shop to faster know which one goes where..
Could be a cable. Try blowing some forced air through to clear dust. If that doesn’t work, it might be loose cable pin somewhere which is a real hit-miss repair attempt. If none of that T-con board is likely failing. Again, not usually too hard to fix but depends on how much room you have to work on the TV.
its not likely the Tcon unless its a connection point between the ribbon cable and the tcon, its more likely the start of a failure between the lcd panel and the board that mounts permanently to the top of the lcd panel. sometimes applying gently pressure along the edge where the bonded ribbon cable that comes out of the edge of the panel will result in correcting it. if it does some people have used various "shim" methods to apply pressure permanently.