"There is an apparently new iOS 18 security feature that reboots iPhones that haven’t been unlocked in a few days, frustrating police by making it harder to break into suspects’ iPhones
…
Apple added “inactivity reboot” code in iOS 18.1 that triggers iPhones to restart after they’ve been locked for four days"
Ah, I don’t use my personal phone for work stuff or my work phone for personal stuff. GrapheneOS also only supports Pixel phones.