Adding onto this. I found deleting the session.state and session.state.bak in the .config folder fixed the issue for me. The logs from journalctl Started Deluge Bittorrent Client Daemon. Deluge daemon 2.0.3-2-201906121747-ubuntu18.04.1 Successfully loaded session.state: /var/lib/deluge/.config/delug...

I keep getting this too and found that it would "fix" itself if I restarted deluge. I'm using systemd to manage the service so I configured the service to restart every 24hrs, that way I don't have to think about this problem

Figured it out. Not ideal but meh
and then put both on hold to avoid upgrading

I just ran into this issue as well. I'm on Ubuntu 18.04. I'd add this to the bug tracker but I don't know how. I'm not very familiar with how package management is supposed to work, but how can I downgrade python3-libtorrent or install an older version of qbittorrent?? I can't figure out how to do t...