After replacing my weatherstripping mine still had a slight whistle to it, just had to adjust the latch a little so the door shut tighter and it stopped.
Yeah, its a 2K hertz whistle. I've added stick on stripping, now i'll try that adjustment to make the door close tighter. Hope that works. It's pretty loud.
Found the whistle....get some clear packing tape and run it up the awening leg from about halfway up throught the curve. on the front side in the crack...That is the whistle....Wow super quiet now....Has nothing to do with the door.
Same situation on a trip to Georgia, Camping World worked on it for 6 hours, and bent our door and couldn't find the source of the whistle. The dealer we bought the rig from knew exactly what the problem was, the awning. They plugged the hole in front of the awning at the top. Problem solved!!