If you're on the latest SDV version, you could try copying your farm save file (located on your device in the Files app > On My iPhone or On My iPad) to iCloud, delete and reinstall the app, and then copy your save file back to the SDV folder on On My [Device]. Deleting the app will delete the SDV folder so important to save your farm save file to a different location temporarily.
Saving it routinely to iCloud or another location is also a good way to keep it backed up.