We've run into an issue in Sitecore 9.3 where it's not serving media items properly via Azure FrontDoor with caching enabled. (Front Door works exceptionally well for 99.95% of the website).
But a 20MB PDF from the media library won't properly download, yet uploading it to the file system and loading it as a static PDF via Azure Front Door file will load correctly.
I have a feeling there's a glitch in the Sitecore media handler chunk capability (Sitecore.Resources.Media.MediaRequestHandler).
Azure Front Door "Delivery of Large files": https://docs.microsoft.com/en-us/azure/frontdoor/front-door-caching
Front door downloads large files in 8MB chunks. It appears Sitecore media handler won't properly serve media items to Azure Front Door when they are > 8MB.
Has anyone run into this issue and been able to resolve it?
I opened a Sitecore ticket, but they can't dig much further into it because Azure Front Door isn't listed in the official support matrix.