Sorry to chime in - I’ve just had this download problem happen to me on Windows 10.
Not sure if OP was using Webtorrent, but this is where it started for me. The torrent would finish downloading on Webtorrent, but like the OP i’m unable to download the finished file. Nothing shows in downloads but i do get the never-ending green bar going through the Brave icon on taskbar. (As if it is downloading something, but it isn’t)
Another small problem is after Win10 boot up. The first time i open Brave, it crashes everytime. (opens and then closes really quick.) - Works fine 2nd attempt.