I completed upgrade successfully and with all new flight modes enabled and Horizon tilt issues corrected. Usinging IOS and Ipad 2 Air.

1. Insure aircraft and RC are fully charged (important).

2. With aircraft off, update RC using DJI app. Make sure you are logged in and have a good wireless internet connection. Once RC has completed update power off RC and IOS device.

3. Format SD card in Aircraft. Connect aircraft to PC using USB to micro USB cable. Power up aircraft. Start up the latest version of DJI assist 2 and install new update.

4. Once the update is complete power down aircraft and remove battery and insert your second battery. Power up craft and refresh DJI Assist 2. The firmware will update battery. As soon as all your batteries have updated, power down aircraft.

5. Power up aircraft and then the  RC. You should have a good link between RC and aircraft, all new flight functions and Horizon Tilt should be resolved.

6. Check all setting and re-set as desired and recalibrate sensors, IMU and compass.

7. Fly safe and enjoy.

I would agree that the Horizon is fixed (at least for now :-) ).

Sure, I'll give it a try tomorrow and let you know. Guess I'll cache maps, so I can locate myself. Why would I ever want to fly my drone without a pipe to the net? Oh right, let me check my underground bunker and my stash of canned food. Man the paranoia has to stop. I'm fairly sure in the long run DJI has ours best interest at heart and their best business interests as well.

It went completely as expected, with no internet connection. Anything specific you would like know?

Need to add my flight is not eradic as a bunch of folks responded, but I am getting the erroneous high wind warning.

What is the need to refresh the update with all batteries when the release notes say nothing about a battery firmware update?

fans26405633 Posted at 2017-7-12 20:06
What is the need to refresh the update with all batteries when the release notes say nothing about a battery firmware update?

DJI Assistant 2 indicates that the batteries need updated, the only prompt for the update is that it shows 'Update' if needed, and 'Refresh' if not.

As you say it is not mentioned at all in any document (or I've not seen any).

I didn't notice battery update was not mentioned in the update narrative. However, when I updated I just assumed the batteries needed to be updated. So when I powered it down and put a new battery in it it performed a another quick updated.

how to download this app? can it be installed on a mac? i noticed my hoirzon is not level on my phantom 4 pro

Yes it's available for Mac.
https://www.dji.com/phantom-4/info