Hi.
I'm trying to load a PDF from an external site which I'm also the owner of (Azure App Service). I've added the following headers to all my requests but I get an odd chain of requests whenever I try to load external PDFs.

Headers:

Access-Control-Expose-Headers: Accept-Ranges,Content-Encoding,Content-Length,Content-Range
Access-Control-Allow-Headers: Content-Range,Range

As you can see I get the initial 200 OK just fine followed by two 200 OPTIONS requests. Finally it alternates between 200 and 206 which isn't the expecte behavior.
When I tested it on a local site the initial request got a 200 response followed by 206 until the PDF had fully loaded.

What obvious thing am I missing here?

Configuration:

• Web browser and its version: Any browser (tested on Chrome lastest, Microsoft Edge lastest, Firefox latest)
• Operating system and its version: Windows 10, 1809
• PDF.js version: v1.9.426
• Is a browser extension: No

What is the expected behavior? (add screenshot)

What went wrong? (add screenshot)