If your app is freezing or crashing, whether during login, when importing, or during the signing process, please try clearing the application cache from the device settings. A screen recording showing the clearing of cache is attached with this help article. 

Please reinstall the app if it is still an issue after clearing the cache. Sometimes an update might go bad, or some corrupt data might cause issues. A clean install will usually clear the issue. Your settings and documents will be saved even if you reinstall.