If you set up your Vault and then left the same tab open, the Vault locking itself after a spell of inactivity left that tab stuck. Your correct Vault password came back as "That Vault password is incorrect", and the recovery key then failed with a technical message instead of an explanation.
Nothing was ever wrong with the password, the recovery key, or the saved items - and reloading the page fixed it. The tab was loaded before the Vault existed, so it never picked up the encryption settings it needed to unlock, and it had no way to notice.
That tab now receives those settings the moment the Vault is created. If they are ever missing, Vault says so and asks you to reload, rather than blaming the password.
Vault also no longer prints raw technical errors onto the form. Messages meant for you - "That recovery key does not match its checksum", for instance - still appear as they did; anything unexpected now shows a plain explanation and logs the detail to the browser console instead.
Elsewhere on the page: Lock and Export are named buttons rather than emoji, and the locked screen has lost its padlock.