Between 8.2.1 and 8.3.x the FTP scheduled backup process failed to initiate.
SonicWall was able to reproduce this issue in the lab and have come out with the probable cause and by its definition, a work around.
Root cause for this issue is any one of the following:
Schedule Name contains a space.
FTP password contains any one of the following: '&', '(', ')','<','>' and ';'.
If your FTP profile contains any of the above mentioned characters please delete your existing schedules and your FTP profiles, and then recreate both. Any scheduled FTP backups should complete successfully.