finished downloads not finished

[Matt1234]

Recently, I have been having this problem in almost all of my downloads. I start a download, and it finishes, but then when i start (in my case) watching the movie, there is a file error halfway through. Then i restart the download with the same torrent file, it starts checking the file, and turns out that the file is not completely done. They restart at various percentages, usually between 60 and 90%, but today I had one that started at 9%. I don't know if this is a problem with Bittorrent, or a different problem altogether.