If there is insufficient storage space for an operating system upgrade, iPhones may experience update problems. To make sure this isn't the cause of your iPhone 8 problem 4013, consider deleting certain apps or transferring images, videos, and other non-system vital files to your computer or iCloud. After that, try updating your device again.

1. Select Settings.
2. Select General.
3. Tap iCloud Storage & Usage.
4. Select Manage Storage.