Carbon Blue

Hey all, Ive had a sony dsx300 HU for about 5 years now paired with a modifry DCI. Lately the OEM volume toggle switch has either been working or not. When I toggle up on the volume to increase sound the HU emits a beep which I can hear but the volume does not increase. Would it be safe to say that the HU is going bad? Everything used to work perfectly fine, all other OEM switches including the MUTE button work fine as well.