I was streaming some video content in my HT two nights ago and during one of the shows every speaker in my setup started emitting this very loud high pitched distorted screeching sound. I tried multiple sources and cables and every source has the same weird distorted sound. I reached out to Denon and they are advising me to send my unit in for service. I did try unplugging from power and plugging back in after a couple of mins. Any suggestions from the pros here?