I might have a simple solution for you. This is simply what worked for me. I was using the pitch glide to play drop c (-2.0) on my guitar that was tuned to drop d. But when I played, I could hear both the dropped notes, and the normal ones. I discovered that it was because I could hear my guitar as well as the amplifier. You might be hearing your actual strings being played. Try using some headphones and see if it sounds fine on those. When playing with your amp loud, you might not be able to hear your own guitar, I haven't had the chance to bring my volume up lately to test it myself.
