I have the same unit and mine clearly makes the sound when disconnecting. Sorry that I have no advise on solution other than to say try and take it back with several items on your check list. I will share one problem that we are having addressed in early December after this trip, we have a water leak in driving rain between the truck cab and the coach. It drips down right on top of the driver and passenger outer shoulders. I suspect that it is a caulking issue, so watch for that. Love ours so far!!
Dave and Anita
2015 Itasca Sunova 33C