I have 17 downloads that range from 99% to 6% completed and then they stop. Why does this happen?

will it depends on what you're downloading or the download peers and seeds

examine the details for each torrent.

Select torrent, right click, then click Properties.  What does it show as "Available Copies?  Is it less than 1?

If there is at least 1 available copy in the swarm, then look at The Peers tab to see if there are connection issues.