Attempting to use real time sync in a profile that is connecting to a remote FTP server seems glitchy. Ideally, if there is a one way sync then the FTP location on the right should only be contacted when there is a new file on the left to send. Instead, the FTP site seems to be repeatedly contacted even when there is nothing to be done possibly causing connection errors with the FTP login. I have avoided these problems by using a 5 or 10 minute schedule instead of "real time".
I believe I have found a specific copying bug. Below where you select the directories to Sync in a profile, there is the option to "include subfolders" with either none, all or selected folders as the choice. I have found that selecting "none" does not work properly when real time synchronization is scheduled. Instead, the entire subfolder was mistakenly copied outbound to the FTP location as if ALL had been selected. The problem was resolved after scheduling the profile to run every 5 minutes instead of real time. I have put a new test file directly into the subfolder to confirm that this is not sent, and the issue is resolved. No other settings were changed in the profile.
I have worked around these issues, it just seems this functionality around real time copying could be improved. I am on version 6.72b.