App is really not crashing, can happen that suddenly stop work, and it's a know Apple iOS issue not only for our App, and Apple recommends actions in that case as are in the link, I posted above. iOS is only program, and can have bugs as well.
Update do not need any special notes. Update updates the unit firmware for a new version. The update does not impact any previous settings in the unit.
Regarding the setup, you mentioned, I'm honestly confused. Please give me more details. The mode of gyro is not controlled by the app, but by the gain signal from TX.
Here is screenshot, please try to explain your issue on the screenshot as example.