Then next I would examine the redirect and check your stack, is it a 302, 304, etc, is there a service identifying header with the redirect?

After that I would try to completely change your setup for testing purposes, greatly simplify things removing as many variables as possible, maybe setup an api server with a single route on express or something and see if that can be faithfully served

If you can’t serve with even a simple setup then you need to go back to the drawing board and try a different option