When using rsync you may encounter the problem that it sometimes stops in the middle of a transfer with no visible reason.
If you ask Google you will find out that also others have this problem occasionally. Unfortunately, the reason and the solution is hidden and hard to find within these articles.
I neither could find the actual reason but it is definitely a matter of the destination file(s) where to you sync the data.
The solution is to delete the file (or even the whole directory) where rsync stops. Then restart rsync and it will work like a charm!