Electrical interference can falsely trigger a touch event and may make the touchfoil unstable or unusable. You can tell if the touchfoil is being affected by electrical interference by going to the graph tab within the provided driver and checking if any bars fluctuate rapidly. The driver may not be able to compensate for this interference and adjustment in the physical setup will be required.
Whilst setting up the touchfoil we highly recommend that you ground the black lead attached to the USB cable to filter any noise affecting the controller board. Another thing to consider is to connect a common ground to the display chassis and any other nearby electrical equipment.
Another cause of interference can be from electrical mains. The effect of mains interference differs in each location but is clear from a consistent fluctuation pattern on the graph. It can be filtered using a mains filter such as a 6 way mains conditioner from UK based Lindy.