I did the upgrade (plus RC and 4 other batteries) yesterday and all went well. Decided to do an IMU calibration today before the next flight - I haven't flown for a week. When I turned on the I1 I received an error message in the app stating under Overall Status on the Aircraft State display, saying that there was a problem and to repeat the upgrade. I got the continuous beeping you described before I repeated the upgrade. All seemed well again after the upgrade until I reloaded my usual SD card, which had an "old" .bin file and other upgrade files on it, and the I1 wouldn't connect to the RC. I then tried another SD card and all went well. I then reformatted the troublesome SD card and all worked well with it. I appreciate this is slightly different to your situation but from now on I will be upgrading with an otherwise empty SD card and flying with SD cards that have no upgrade files on them. I feel that if the app says Normal for Overall Status, the IMU has been calibrated and the sensors give appropriate readings you should be good to go.