RTRR/FTP sync from QNAP to Ubuntu desktop.

[Boyturtle]

I am trying to run RTRR on my TS-251+ (v. 4.3.3.0262) and my Ubuntu 17.04 desktop, both sat on the same subnet. The goal is to sync a number of folders on the NAS to /mnt/Backups on my desktop. I use Proftpd as the ftp server on the desktop.
When setting up the sync job in Hybrid Backup Sync >One-way Sync> Create Sync Job> Sync Local to Remote>FTP and set up the job with the above settings, syncing does not occur (when I test it in settings, it shows success). When I look at /var/log/proftpd/proftpd.log file it shows a constant and continuous ftp session opened/user x: login successful ftp session closed. The log file continues to expand until I stop the job.
If I then go into the proftpd.conf and change conf to jail all users in their homes and then set up another job that points to a folder in the /home/userx directory and the RTRR syncing works perfectly.
Looking at ownership and permissions on /mnt/Backups and they are identical to /home/userx (userx owns both).
I have also tried vsftpd with similar outcomes. I have been backwards and forwards with QNAP support for more than 6 months on this issue and the problem has been consistent the previous 3 or 4 builds since I first tried to set it up. QNAP are seemingly unable to assist me to resolve this.
What am I doing wrong here and why can’t I get the syncing to work to the location I want them to write to? Any pointers greatly appreciated.

[Boyturtle]

It looks like the chaps at QNAP finally came good. RTRR is now working correctly and replicating as it should be, so I am delighted.

Unfortunately, I do not know what caused the problem, or what the fix was; although it would be nice to know in case anyone else here had a similar experience.