I ran into an issue where if I ran rsync to a remote server with a path that contained spaces it would simply terminate at the first space instead of copying the whole path. I learned you need to do some quote tricks to get this to work properly (thanks to this site for helping me.)
The trick is to enclose the entire remote path, server included, in SINGLE quotes. In addition to the single quotes you still need to escape every space with a backslash ( \ )
rsync -aP <source_folder> 'REMOTE_SERVER:/full\ path\ with\ escaped\ spaces/folder/'