When attempting to work on an application via a RIM node the environment, you see errors when attempting to use extensions that work when accessing the application on the central node.
The app can be accessed/edited without any problem. This issue happens when the Proxy Node that is being used within the Virtual Proxy does not have access to the Shared Folder where the extension are stored. IE: \\QlikServer1\QlikSP\StaticContent
Make sure that ALL of the nodes are using a service account that has access to the Shared Folder path that is being used by the clustered environment
If a node is using "local system" as the service account, it will not have direct access to the Shared Folder and it will not have access to the Extension folder.
(unless within the folder security "Everyone" is applied and the services are within the same network)