Hello [NAME], As far as I know, the only method is the one you already mentioned. However, I have seen some errors when upgrading by GUI and were shown as Connectivity failures (upgrading to 5.14). So I suggest you opening a case directly because they might need to check the logs and perform some operations directly on a remote session. Regards.
I have more than one customer experiencing upgrade issue with webUI. SCG servers have connectivity to Dell Global gateway servers on required ports through Proxy but due to their internal security requirement, installation package not allowed to download through SCG server, which means customer cannot download installation package with webUI. May I know any other methods to upgrade except re-deployment?    
SCG unable to upgrade from 5.12 to 5.14