

Was this pc running Linux by any chance? I was in exact same scenario a few weeks ago. But only after I switched to Linux. Before that, never had any issues with protonvpn (or any VPN) and qbittorrent.
No problems since I did the same thing you did. Set qbittorrent to use only the VPN connection.
The point is that the killswitch doesn’t seem to do much, at least on Linux in my experience. I’ve never had it work.