Being blocked by Brave when trying to upload files

Description of the issue: I am using a cloud-based reference manager called Paperpile (for keeping track of scientific articles) which is designed for Chrome, but has previously worked flawlessly with Brave. It still works for the most part, but if I try to upload a pdf from my own file system, Paperpile throws an error, says it does not have permission to store temporary files using the browser’s file system, and points me to the following troubleshooting guide:

https://paperpile.com/troubleshooting#file-uploads

Now, I have a fair amount of trust in Paperpile, so this is with Shields down and whitelisting in the cookie settings.

Steps to Reproduce (add as many as necessary):

  1. go to paperpile.com (paid service, user required)
  2. choose Upload Papers from Add Papers menu
  3. pick any local file

Actual Result (gifs and screenshots are welcome!):
Error message: " Whoops — Paperpile was denied access to your file(s). This can be fixed in your Chrome settings."

Expected result:
Upload of file.

Reproduces how often:
Every time.

Operating System and Brave Version(See the About Brave page in the main menu):
Brave Version 0.68.142 Chromium: 77.0.3865.90 (Official Build) (64-bit) running on Ubuntu 18.04.3 LTS.

Additional Information:
Tried it on Chrome and it worked without flaw, so that points to it being a Brave issue.