This is for anyone having the Ultrasound emergency problem out of the box. I was getting a lot of this for the first week of flying and it was really frustrating. Fly for a minute then crash then fly for a minute and crash. My drone was doing this even over high contrast areas and with the ultrasound emergency the props stop flying so you might as well just hit the emerg button yourself.
What I did to fix the problem.
I suspected that the Nav board was ok as my drone was doing this out of the box and all of the seals were intact (never been flown). Eventually I built up the nerve to peel off the plastic bottom and take a closer look of the nav to main board connections. I removed all three connection points and removed the nav circut board. I found that the pressure sensor (it’s the black square with a bit of foam visible on the top) on the top side of the board was partially peeled off. I re-stuck the black pressure sensor to the board and took a photography blower to the metal ultrasound sensors to clear any possible dust that had collected in them.
After reassembling the drone took it for a flight and viola, fixed works like a dream now. No ultrasound issues whatsoever since the fix, now if only Parrot would send the new software so I could get off .18 (stupid drone drop).
A word of caution to anyone removing the nav board from the main board. Be careful with the plastic retaining clips, they are only very thin plastic and break really easily. Remember you are probably going to be re-using the nav board and will need those clips later.
Hope this helps
iPhone 4 IOS 6
Firmware 2.1.12 and never going to change...EVER