Please provide the following information
3.3.7 in Fedora 25 64
As far as I can see my active torrent is being downloaded by at least 60 people simultaneously
15 as indicated by maximum number of upload slots per torrent
none, just seed
Perhaps it's a problem with libtorrent but I'm just reporting.
Do you see the capital U flag on more than ~16 peers at once?
Little u flag only means that they want to download from you ...but are currently waiting for an upload slot to do so.
Residual upload speed happens to peers qBT was previously uploading to for possibly 10-40 seconds after last sending them any parts of the torrent.
Small (<1 KB/sec) amounts may also go to/from them due to PEX and HAVE messages.
It's possibly a very bad bug if you don't see a u or U flag to a peer but it is downloading from you at >2 KB/sec.
I'll check it out but from what I remember at least 50 peers were downloading at speeds above 4K/sec. With libtorrent 1.0.10/qbt 3.3.9 I definitely don't see this bug.