This happens to me every few months for the past year or so. I can't get qBittorrent to start properly, it just hangs. No amount of Mac restarts or qBittorrent restarts fixes it. Then it usually starts to work normally again after 2-4 days.
It has been reported here, and on GitHub and for some reason it still hasn't been fixed. I suspect, but it's just my wild guess, that there is some external tracker condition which triggers this error and that makes it very hard for developers to reproduce because they would need to be sharing the same problem torrent to replicate the issue.
Try reporting the bug here:
https://github.com/qbittorrent/qBittorrent/issues/14360
Fingers crossed that 4.4 solves the problem!
(Intel MBP)