Even if my observations amount to nothing more than anecdotal evidence, this is an educated guess:
- Screen touch issues occur only when charging via the USB port.
- If the contact pressure on the USB port is increased—for instance, by inserting a thin shim—the screen touch issues disappear.
- If the USB port is replaced, the screen touch issues cease to occur.
Of course, this could also be due to a defective mainboard, a loudspeaker manufactured with incorrect tolerances, or even cosmic radiation.