When installing Symphony on top of a running EGO cluster, there are errors in the GUI tomcat log, how serious is it?

This will only happen when you install on top of a running EGO cluster. The error can be ignored in this case. As long as you restart WEBGUI, the Symphony page will be added to the GUI and work properly.

As a workaround, stop WEBGUI before you install new component on top of an existing running EGO cluster.