I did the upgrade to RC 1.6, and it seemed to go well. iPad Mini 4 on iOS 9.3.1
After powering up the RC later, it showed Upgrade Required again. I clicked to install, and it started but this time the screen showed Current version: Unknowm, Upgrade Version 1.6.0
After beeping for at least 30 minutes, I came back to the Go screen which no longer showed the upgrading dialog.
So I powered down the RC, and now when powered up, it shows the red LED for about 15 seconds then it starts flashing and the RC beeps. The Go app shows "Remote controller connected, please connect your aircraft.", but of course the RC does not connect to anything because it is too busy beeping!
If I go into "Linking Remote Controller", the beeping tone changes and the status LED changes to blue, but never responds to the AC even after pressing the link button on the AC.
I have tried reinstalling the Go app, charged the RC battery to four LED's overnight, calibrated the sticks.
Is there a way to reset the RC to a state that it will take a firmware upgrade again?