This crash was happening regularly, sometimes as often as every 10 minutes. The Apple Store first recommended we wipe the device of all data and NOT restore from a backup. Problem still happened. Then the Apple Store replaced the device, and again we did not restore from a backup, and again, the crashes quickly resumed.
No restore from backup. Brand new hardware. Same crash. Diagnosing this just got interesting.
It turns out that Apple’s TextInput service uses Core Data and iCloud to store user dictionary entries such as shortcuts/abbreviations. His database became corrupt, which caused SpringBoard to crash. iOS doesn’t have any way to clean out this data, but he was about to do so from a Mac by digging into the Mobile Documents folder.