Apparently, there is a date bug in iOS 11.1 that has affected a number of apps, including DJI GO and DJI GO 4. This may lead to the apps crashing. DJI just issued an official announcement addressing this issue.
Official DJI announcement
Dear DJI User:
The date bug in iOS 11.1 has affected a number of apps, including DJI GO and DJI GO 4. Users may encounter instability or crashes when using these apps.
To fix these issues, we suggest trying the following troubleshooting steps: 1. Apple recently released iOS 11.2, which contains potential fixes for the problems mentioned above. Try upgrading your Apple device from iOS 11.1 to iOS 11.2. 2. If you want to continue using iOS 11.1, sync your flight logs, save all your photos, videos and other data you need, and try reinstalling DJI GO. 3. If you still encounter performance issues after your device has been updated, please contact our after-sales support team. Our app development team is working to release new versions of DJI GO and DJI GO 4 in order comprehensively solve these issues.
Thank you for supporting DJI, and we are sorry for the inconvenience.