There is only one scenario that can cause this problem: when you move, change or delete the file from the downloaded or default location. In this case, when you open the 
Torrent Pro app, it will check for the completeness of the torrent file and if anything is missing, it will try to download the missing part. To avoid this, you can either pause the torrent or delete it from the list. Please refer to the image below for more details.
