2FA not working due to JWT issue

[lisams]

When activating the 2FA in Shopware Backend for new profiles, an error occurs in the console:

[
    {
        "code": "9",
        "status": "401",
        "title": "The resource owner or authorization server denied the request.",
        "detail": "The JWT string must have two dots"
    }
]

The error occurs with the endpoint /api/rl-2fa/validate-secret.
We have the issue for an instance of SW 6.6.9.0 and SW 6.5.8.13.
There are no errors in the server log files.

Thanks for taking care of this issue!