I have recently discovered that on initial load, the WDQS database was by mistake loaded without sitelinks. Also, there were a number of small changes in RDF format since July which may need the update.
Due to this, I plan to reload WDQS servers from fresh dump. The functionality of the service should not be affected as the server being reloaded will be in maintenance mode and will not be serving requests, while the other server will serve all requests.