I was trying to recalibrate my Denon 3910 but the test tones are not constant. They Buzz, stop, Buzz, stop etc.. Has anyone else experienced this issue. I do have the most recent firmware upgrade. Test tones worked before I installed the "upgrade" but I installed it months ago and never re-checked the test tone generator. Hence, I don't know if there is a cause and effect relationship. Any help will be much appreciated. thanks.