CORS partially fails when making requests with axios in React

[AdolfoRoquero]

I am using React for the front-end running on 'http://localhost:3000' and Flask for the backend running on http://127.0.0.1:5000.
I am running into the following error
Access to XMLHttpRequest at 'http://127.0.0.1:5000/manager/personnel' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: Redirect is not allowed for a preflight request.
I am using the following code to set up CORS:

cors = CORS(origins=['http://localhost:3000', 'http://127.0.0.1:3000','http://localhost:5000'])
...

def create_app(config_class=Config):
    app = Flask(__name__)
    ...
    cors.init_app(app)

I also tried using CORS at the blueprint level unsuccessfully.
What is most surprising is that some requests to the backend still succeed.

Someone had a similar issue on StackOverflow but never got a response: https://stackoverflow.com/questions/73665955/why-do-i-get-a-cors-error-with-react-axios-and-flask

[Aadesh-Baral]

Does this URL http://127.0.0.1:5000/manager/personnel exist on your backend app? Can you verify it's http://127.0.0.1:5000/manager/personnel without / at the end ?

[JacobDel]

same problem, with or without "/" at the end

[terrynguyen255]

Seems related to this unresolved issue.
I will update this comment if I can figure it out.