When changing the password, set how long you can still rollback to the old password.
At Keepass and box.net I already had what I did wrong with the Master Password Change. Or had forgotten it within the first 48 hours I could still restore the backup.
You could do it without losing security. With an optional time for the storage period of a backup of the data with the old master password. Or one could optionally still offer after the login with the new password the next 30 days offer to delete the backup by button immediately.
Implementing this securely is hard. Your master password is not supposed to be saved anywhere except in your mind and maybe in a safe deposit box. The old master password would have to be saved somewhere.
LastPass does something like this by saving an encrypted one-time password on your local device (if so configured in settings), and requiring email validation to decrypt it. It gives you a little extra safety with a little less security.
If something like this is done, then a more generalized mechanism than last 30 days would be desirable.
In the mean time, you can get a free Dashlane account and enable emergency access to it, and have a single entry in it that contains access information for your Bitwarden account and any other instructions. This allows password recovery if you are really stuck.