Vertical Deflection problem. Over the last few weeks my TV has come on with either no problem at

Question

Over the last few weeks my TV has come on with either no problem at all or a thin bright line across the middle. (Left to right) If we hit the set from the sides it would correct most of the time. I know it is a vertical deflection problem from other web sites but what component should i be looking at for re-soulder or replacment. I pulled the circuit board and poked around and found nothing obvious or repeatable. Read that it may be a cold solder or bad cap but any clues where to start looking? Flexed the circuit board a little as well and nothing repeatable.Thanks