First, if you have not already done so, clean the screen, depending on the type of touch even a piece of dirt could activate it.
Second, get a thin blade and lightly run it around the screen, where the touch meets the plastic/metal casing.
Third, if you can get to calibrate the screen do so otherwise perform a factory restore, if it is android, power off the tab, hold Vol + and power on, let go of power once it comes on and keep the volume button pressed, usually touch is disabled in restore mode so you have to use the machine buttons to navigate and enter. I had to do this to fix a Alcatel OneTouch phone so it is worth a try.
Forth, if all else has failed you may have to disassemble the tablet, it would appear there is a pressure point on the screen which is actually banding the screen causing it to make contact with the touch panel. Not knowing which tab it is I cannot direct you on disassembly but it is generally a simple enough process.
Before trying this part, run your finger around the edges of the screen, with slight pressure, if it has had a fall or a bang a clip for the screen could have popped out of place and just needs to be seated back in.
This is all the help I can give, try them and see if it helps.