Welcome to Android Central! From what I can tell on their website, those buttons are capacitative buttons, and not related to the touchscreen. Does the problem persist after a reboot? Or booting into Safe Mode? To boot into Safe Mode, from a powered on state, press and hold Power until the Power Off menu appears, then press and hold Power Off until the Safe Mode prompt appears. Then tap OK. Safe Mode prevents all 3rd party apps from starting, so this can tell you if something you installed is causing the problem.
If none of that works, you could try a factory reset. But it's likely that there's a hardware problem with the buttons, and you'll have to bring the phone back to the store or contact Kata.