To be fair not sure if its related with the .0400 firmware upgrade but I received the mentioned error today during my 4th flight ... I checked by filming the mavic from the front and top - seems like its no longer emitting - have seen others reporting it on other forums and was wondering if this is potentially an early batch issue ... I downgraded to the earliest firmware and tested all versions - no error message but the same behaviour...

Its simple to identify - video the mavic from the front or top and you should hear the knocking sound like in this video when you play it back   - now my mavic is dead silent ...

As I also have the camera issue where one area isnt in focus I hope I can get it RMA'd in one go - quite annoying though as I just started to enjoy the little thing - not to mention the wait time for it ...

Anyone else seeing this?
Referring link "Ultrasonic Module Error" since updating to 01.03.0400

http://mavicpilots.com/index.php ... 514257&share_type=t

I got this error earlier today. I found an old post on a forum from a few years ago by a guy who had a Phantom and DJI support said "try calibrating the compass and IMU... if that doesn't work send it in." About 45 minutes ago I tried that and the error went away... at least for now. I've only taken it up for one flight right now so we'll see where it goes from here.
EDIT: Oh, the knocking though... Mine didn't do that. Not from what I could hear. I'd keep my eye on that.