Creating a backup from Firefox causes connection loss

What type of hardware are you using: VPS bought online
What YunoHost version are you running: 12.1.15.1
How are you able to access your server: The webadmin

Describe your issue

Creating a backup from Firefox causes a connection loss.
The backup process is successful, but connection losses happen almost every day, since I perform a backup before every upgrade.
Is this problem common to everyone?
Thank you.

Share relevant logs or error messages

none