To confirm it is the tft screen connect external monitor and ensure that fault does not occur on the monitor?
Did a quick check on tft screen prices
here and they appear to be quoting a lot less assuming your screen is 14" or less.
Another possible cause may be the backlight playing up
Would also suggest moving screen to various positions and each time try to reproduce fault. If it only occurs at certain angle could be a prob with the tft data/power cable that runs from the system board to the tft screen