OK I have solved the problem. But only by completely uninstalling X1 Search including deleting the index and removing all settings, rebooting and re-installing v8.3.2.
This is slightly irritating being as I now have to rebuild all ms settings and all my bookmarks. And I now have to wait while it rebuilds the index from scratch.
This is slightly irritating being as I now have to rebuild all ms settings and all my bookmarks. And I now have to wait while it rebuilds the index from scratch.