Solution :
As far as I know, your Chrome was expecting some of the material that it could possibly display (e.g. a document), but it received something which it could not display. This is both the question of how a document was declared at your HTML page level in a href and how it is declared within your server's answer by this means of HTTP headers so this is the question of contract, as opposed to the hope and expectation.
I have experienced that the :
Content-type: application/pdf
Content-disposition: attachment; filename=some.pdf
is just very inconsistent with your:
<a href='some.pdf'>
Here Chrome will definitely cry as Resource interpreted as document but transferred.
Actually, your attachment disposition clearly means that: your browser must not interpret your link, but rather it should store it somewhere for the other purposes. So above, either the download is missing besides the href, or Content-disposition should be removed from the headers.