Since Share Simplification changes to the user menu in the top title bar, the Cloud build of Share 5.1 no longer adds the Cloud specific menu items to the menu. I suspect the cloud override cannot find the menus items in the order/IDs that used to be there. e.g. Network Admin menu item for those users.
See share-header.get.js override in root/privatemodules/thor-share/config/alfresco/site-webscripts/org/alfresco/cloud/core/customizations/share/header/share-header.get.js in thor-share project. I suggest the other Cloud Share overrides are checked.