Onkyo TX-NR1009 volume level

Just hooked up an Onkyo TX-NR1009 receiver to four HDMI sources: DirecTV, Oppo DV-980H DVD player, PS3, and ACER Revo HTPC.

Overall very happy with the TX-NR1009 with the exception of one issue. When I turn on the Oppo, or open and close the tray, while watching DirecTV, the volume level on the speakers of the DirecTV program I am watching oscillates, meaning the volume level goes down for about 5-10 seconds and then it goes back to the previous level it was set at. This happens all the time.

I switched HDMI inputs using different cables. Then I also switched to another model Oppo player and still does the same thing. However, it went away when I switched to a Panasonic brand DVD player, the oscillation went away.

Onkyo tech support says it is not the receiver. Oppo does not think it is their player, nor do have a solution.

Any thoughts?