Guest User Prompting For Keychain Password--but I never set a Keychain password. Renders guest account unusable due to incessant prompting.

I never set a password on the Guest account (can you even do that?) and nobody (to the best of my knowledge) ever set a keychain password. Even if the Guest account users did set a Keychain password, none of the Guest account users know it.

How do I recover?

I have tried Keychain First Aid.

I have tried Repair Disk Permissions.

The endless prompts is effectively a denial of service attack on the guest user on my machine. Messages, especially, prompts ad infinitum.

I'm not even sure why a "stateless" account like the Guest account has a keychain. The warning at Guest logout about deleting all files every time you logout from the Guest account must not apply to the keychain.

Is there a "Delete User/Add User" sequence I can go through to get the Guest User Account Keychain squared away?

This problem may have appeared after I enabled iCloud keychain syncing on a non-Guest account. Is that related to this? Or just coincidence?

Any successful recovery paths suggestions appreciated.