Nautilus automatically disconnect sftp connection after a few minutes

Question

According to this article, I used Nautilus to connect to a sftp server. On Ubuntu 19 this package was already installed, so it seems a good way to use sftp directly in gnome's file app. So no external software like Filezilla is required.

This worked well, but after a few minutes the connection automatically got disconnected and the ressource disappears in the files app. For me this is a problem since I'm using sftp on a server where I want to work with Wordpress customizations. I should be able to work for a few hours without interruption.

What is the cause of this disconnect? I don't get an error message. The connections disappears without any information why this happens.

Please note that this is ftp acess for a webspace. So I don't have acess to the underlying server and the logs, which may contains information about the problem.