Bittorrent or any other torrent program (utorrent is better) doesn't download from the start to end. They grab what they can from others who are sharing it. The nearer you get to the end the less the program can choose and when you're at 98% you might miss just one file and nobody is there to seed it.
For example someone is seeding File 1 and 3. Your torrent will download 3 and 1 and when it comes to 2 it can't do anything but to wait and hope for someone to start uploading it.
For example someone is seeding File 1 and 3. Your torrent will download 3 and 1 and when it comes to 2 it can't do anything but to wait and hope for someone to start uploading it.