DB backup not working

Hello,
I have a problem with db backups made via HC panel, with databases stored on a remote Linux machine. When a user makes a backup using the "Backup DB" button HC creates an empty file in the "db" the folder of the website, even if HC shows a message saying that the backup was completed. This problem doesn't happen if the db is stored locally on the same server as the websites.
How can I solve this issue?
Thank you
 
Roberto

My HC version is 9.02