How about if instead of trying to change the eMail-address you just create a new account using that new eMail-address ? Might not be the perfect solution but still a workaround.
If you’re still having issues, we do want to address them.
If it’s time-sensitive and you can’t get it to work, then creating another account is a workaround, but please reach out here: Contact | Bitwarden so we can help troubleshoot and/or create a bug report.