Hello, I picked up a used Genz Benz shuttle 3.0 that seems to have an issue. When connected to a cabinet I am getting a large cone displacement when activating the mute switch or any of the signal shape switches. I took it to a friend with an oscilloscope and we saw that in addition to the switches causing the cone movement as soon as signal from the bass hits the amp we get a dc offset at the effects loop on the order of about 3 volts. The head plays and everything seems to work but it sounds somewhat fuzzy. Is this normal or does it need repair?