iCloud backup crashes Preferences.app

Hey Apple support community,

First of all, a caveat: this issue applies to a device running iOS 6 - if your only suggestion is going to be "update to the latest OS, duh", please save yourself the time of typing that up. Thank you.

So, not quite sure when this started happening, but probably somewhere around enabling of 2FA.

MobileBackup was very temperamental on iOS 6 forever, but this issue is new: iCloud backup was disabled to do an iTunes backup. Upon trying to enable it back on through the Preferences.app, it would crash on the "Enabling" loading screen. Deleting iCloud login from device didn't help. Upon trying to re-login (when already logged on), iOS would present a Recovery Key screen (despite my version of 2FA not being setup with a recovery key, so I obviously had nothing to enter there).

I disabled 2FA, and the problem persisted, just with normal login screen and no prompt for the recovery key.

I re-enabled iCloud via iTunes, and now Preferences.app crashes after about 10s on the iCloud backup page. This doesn't give me enough time to delete an (empty) dummy backup that shows up, but I don't think this is causing the issue.

The logs show it's (obviously) the com.apple.preferences.backup_state thread that brings Preferences.app down.

Not really counting on a fix here, but would anyone possibly know of any changes to how iCloud servers report backup states now?