App suddenly crash when using flask-dance with AZURE AD (CORS policy problem)

Question

I have built a new WEB APP in Dash that authenticate the users using AZURE AD SSO:

And I did note that after some time idle, the app stop to work but it doesn't raise any error, only showing the message that show the info that the server is unavailable...

In the browser console, it is showing the following warning/error:

Access to fetch at ' (redirected from 'http://localhost:8050/_reload-hash') from origin 'http://localhost:8050' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

I would like to know if someone has faced this problem before or if someone knows how to deal with it... I did some searches and tried some approaches but I do not have any idea on how to solve the problem.

Any help on how to debug it will be really appreciated.

Regards, Leonardo