The problem you describe relates to whatever sites and torrents you're using, and potentially your own system's configuration or limitations - it has nothing to do with Tixati, or any other bittorrent client.
Immediate potential solutions:
-Find alternative torrents with the same contents, with more seeds (no miracles, if there aren't);
-Revert your torrent client options to the default, in case you manually altered the number of seeds/peers it can use, or just plain increase those numbers (check the guides below for recommended values).
Relevant info you may need to explore in order to improve your bittorrenting experience:
-Description of the Bittorrent protocol and how it works:
https://en.wikipedia.org/wiki/Bittorrent
-Tixati optimization guide:
http://www.tixati.com/optimize/