Odd issue after installing as service and Duplicati.GUI.TrayIcon.exe

That would depend on what operating system you are running.

But what do you mean by “just 1 install”? Unless you’re using something like portable mode there should only be a 1 install of Duplicati.

Most likely what you are running into is that the service starts and grabs port 8200 then when a user logs in their tray icon starts and, seeing that port 8200 is in use, grabs port 8300.

Each is running it’s own “backend server” with it’s own set of backups jobs. If you wan the tray icon to connect to the service “backend server” instead of starting its own, then consider this step of the Migrating from User to Service install on Windows topic: