Start by comparing the build settings for Release and AppStore. There may be a difference.
Another source of errors may be that you have something on your device (for example, c NSUserSettings) that does not exist on devices on which the application storage assembly is deployed.
The third option I can think of is #ifsomewhere in your code, for example
#if RELEASE || DEBUG
SuperImportantCallToMakeItWork();
#endif
You must have the same testing conditions for the release and assembly of the app store. Reinstall the same device, if necessary.
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