Capacitive touch screens are very sensitive to power noise. Ripple voltage/current from the power adapter can cause the LCD ripples, as well as the capacitive touch malfunction. If you use the APK Multi-Touch under Android to test it, you can find the touchpoint float. There are several ways to solve this problem:
1) Use a high-quality power adapter. Or a battery to provide power like a cell phone or tablet PC.
2) If the power adapter isn’t good enough, make sure the power input connector Pin 3 is connected to the Ground. This method can eliminate the problem totally. You can test it by touching the GND with one hand, while the other hand operates on the capacitive touch screen. In this case, the user’s body acts as the Power System Ground.