Thank you for your quick answer!
When I changed the debug level to 3 I saw that every file wasn’t copied (“php_rsync: failed to copy”).
I’ve changed the wp-content folder to wp-content-temp, created wp-content and temporary set to chmod 777 and then run SitePush on development website en pushed to live. That worked and now SitePush works both ways!
I think the problem was with ownership of the files instead of permissions, because the file permissions are now lower, but the sync works great.
Thanks for your help, great plugin!