I have found the bug. Here are the steps to reproduce. It appears the the development team changed the approach to change the units of measure for wind speed between Android and iOS. In the Android app when you tap on the Wind Speed in Settings a modal pops up with a menu (radio buttons) of units of measure to select.
In iOS tapping on the wind speed (while in the Settings) cycles you through the list of supported units of measure for wind speed (there is no menu / modal popup to select a unit of measure in).
The Weather Flow app v2.5 update defaults wind speed to MPH (potentially only if you had KM/H selected prior to updating the app to v2.5 - I was unable to test that).
Step 1 - Change the wind speed unit of measure in Android to KM/H
Step 2 - Close the app and have it restart
Step 3 - Try to open the Settings in version v2.5 of the App in iOS (app will crash)
To Stop the Crashing
Step 1 - Change the unit of measure in Android to MPH
Step 2 - Open the Settings in version v2.5 of the App in iOS. The app WILL NOT crash and you can set the unit of measure of wind speed to KM/H.
Step 3 - The Android app will not synchronize to KM/H (and will continue to display MPH). The app used synchronize it’s settings across iOS and Android. If you change the setting in Android is will cause the iOS app to crash.
This problem seems to be isolated to Wind Speed from my testing. Upon further testing ALL unit of measure changes in Wind Speed (EXCEPT KM/H) work properly and propagate between iOS and Android apps
PS - I did not try all of the settings. By way of a test I tried to change the temperature unit of measure between C and F on both Android and iOS and it worked as expected. I could adjust that unit of measure on either Android or iOS and the change would propagate across all devices regardless of whether they were iOS or Android.