I think this is a server issue/bug. The client treats all 401 errors as "not signed in errors". Here is the doc for a 401:
The HTTP 401 Unauthorized client error response status code indicates that a request was not successful because it lacks valid authentication credentials for the requested resource. This status code is sent with an HTTP WWW-Authenticate response header that contains information on the authentication scheme the server expects the client to include to make the request successfully.