The error "ServerGui Buffer full, cleared ServerGui logFile Monitor window", is not really an error more a notification and can be ignored. It has to do with the Server GUI this is switched on at your side but can still not be visible, it is a checkbox in the server settings editor.
You can either disable it if you are not using it or to show the GUI in the screen go to windows services, right click on the service desk server service, select properties, log on tab and check "allow desktop interaction". To see the GUI you than need to restart the service.
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