"Some iCloud data isn't syncing" loop after 2FA rate limit / wait it out or reset E2E data?

Ran into a 2FA rate-limit loop during an iOS beta setup. I waited 24 hours n downgraded to stable iOS and logged back in fine with 2FA code.

Now Settings shows "Some iCloud data is not syncing." Entering my old passcode fails with "Couldn't sync data," leaving "Delete E2E Data" as the only prompt.

Does the passcode/E2E verification server have a separate 24-hour cooldown, or is the encrypted key chain actually corrupted?