I recently updated my torrent client to qBittorrent 4.1.0 in order to solve some problems I was having with an older installation and unfortunately introduced some new ones. I think I've figured out what the problem was, even if I have no solution. I'm sharing this information here to save someone else the headache of figuring this out if they encounter the same problem and to see if anyone else has insight for a way to fix it.
Originally after a helpful chat with the helpdesk this appears to be the classic Vuze/ Azureus problems which everyone is likely familiar with. it has similar symptoms and solutions. however this turns out to be a different beast altogether.
The problem in the simplest terms is that downloading works fine, but as soon as a torrent completes downloading it becomes inactive and will never seed. obviously this makes maintaining a decent ratio quite difficult.
Basically the problem has arisen from some basic functionality in qBittorrent that seems to have been broken in its newest updates. Allow me to explain houw I understand to problem to come about. qBittorrent operates off of a queue system where it evaluates the torrents it has on its list and only activates for seeding or leeching torrents it believes are going to be most effective. this way most torrents spend most of their time in the queue with only a few chosen torrents active at any given time to optimize speeds. how this is supposed to work is that it will see torrents that are active but not actually doing anything (or has activity below a certain threshold) and will mark these as "slow" torrents and will then not count these slow torrents against your maximum active torrent count. thus freeing up the slot for another torrent that could begin seeding or leeching.
slow torrents do not seem to work at the moment. even with no activity ona torrent it will not be flagged as slow, because of this the system gets clogged up with torrents that are not doing anything at all but will not move on and activate torrents that could be doing something. completed torrents to be used for seeding are in an even more dire situation, once at 100% torrents get bumped off the queue and no longer have a number at all. as such they are last to be checked and so will not become active.
until qBittorrent fixes this issue, which has been flagged in their bug reports and is being worked on the for the next release, the only solutions I can find are to (1) disable the queuing system entirely under Tools> Options> BitTorrent and then unchecking the box for Torrent Queueing. this solves the problem but is terrible for optimization and torrenting efficiency. or (2) manually force resume torrent you want to seed, which works but requires a great deal of manual input on the user's part choosing torrents to activate and deactivate. Neither of these solutions is ideal, but it's the best I've been able to come up with. If anyone else has insight, I'd be happy to hear it.
It's unfortunate that qBittorrent has made such a fundamental error. I had heard it put forth as the successor to uTorrent after its latest iterations have caused so many difficulties, both from a technical standpoint and from an advertising and malware aspect. it's a sad state of affairs when uTorrents users are forced to run an outdated version simply to maintain a decently functional product. it seems qBittorrent has issues of its own. at least its open source and hopefully a fix will be coming forthwith.