Any suggestions as to why this may be?
Our workaround for this was to have our filter also look the JWT in a query parameter on the URL.
Ideally, that token would contain only permission to download that specific file for certain period of time. That said, one additional filter would have to be implemented to look for token in the URL.
I believe that Amazon S3 is doing the same with signing URL requests for file download (http://docs.aws.amazon.com/AmazonCloudFront/latest/Developer... and http://docs.aws.amazon.com/AmazonS3/latest/dev/RESTAuthentic...)
https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequ... https://developer.mozilla.org/en-US/docs/Web/API/URL/createO...
And then programmatically click the object URL.