What you say is typical for what cannonmc mentioned, you haven't got all the files in a torrent's file list as completed completed download, but only those parts which you've selected to download.
The way you put it "(…) All my parts to a torrent file are downloaded fully. (…)" seem to confirm that. The question is not to have all your parts, but all files of a torrent.
The torrent protocol knows basically two type of peers: Those which got all files of a torrents file list and can seed it all of them, known as Seed/Seeder and the others having not 100% known as downloading peers (or derogative leecher). So if you haven't got all files completely a tracker will count it still into the downloading group. Of course any amount of data you seed will be counted correctly towards your total upload. This is common to all trackers I know (and it are quite a few).
If you say to have got all files (not only those you've selected to download), then it would be interesting to know what torrent client programme and version you use.