I don't think this happened with previous firmware updates, but what I noticed with this one is that it reset all customer settings in the app. I had the Ultrasonic Error early on, on 2nd or 3rd flight, while flying over a forest canopy, 50-60M up. DJI support said calibrate IMU and call if it repeats. I decided, instead, to just turn off VPS. Not problem since. Yesterday, after the update, I got the error again (over water). Returned to land and opened the app settings to turn it off. Later in the same flight, switch to A mode and got message saying I would have to turn on Multiple Flight Mode to use it. I did that after flight one. Looked around and noticed that all of my custom gain and brake speeds were gone too.
It would be nice if firmware updates could cache and reload custom settings to the app. Sure there are possible errors that could happen if a pilot is not expecting his/her P3 to have had settings reset.