Flask App on Chromium Browser - pages being downloaded, sometimes

I have a Flask/uwsgi web app running on nginx in a dedicated chromium browser instance on a Raspberry Pi 3. The app works perfectly fine for the most part, but occasionally when I click a link the page that is supposed to load is downloaded instead. If I click multiple times the page will usually download multiple times, though sometimes a subsequent click will load the page properly. If I refresh the page after a download and click the link again, it will usually work fine.

It seems to start doing this randomly, so I'm having a tough time figuring out where to start debugging this. I'm at least trying to figure out what are the typical causes for something like this, and if would be most likely an issue with chromium, flask/uwsgi, or nginx. Any help is appreciated.

EDIT

When this issue arises again I am going to post the nginx log for the request here. I believe that should be relevant but not entirely sure.