Problem decoding vault

I had my vault data but the ui page shows Problem decoding vault when I submit password and vault data.

Start by reproducing the vault-decryption flow in the UI with the reported password and vault data, if available, then trace where the “Problem decoding vault” message is produced. Confirm the expected vault format and identify whether valid vault data can be decoded; done means the reported case succeeds or the failure is diagnosed with a clear reproduction.

Written by the indexing model from the issue text.