n-Stream unable to find uPNP server, or taking a long time to get songs - QNAP HS-210

Hi, I recently got a QNAP HS-210 NAS to go with my Superuniti, and I find that n-Stream regularly loses connectivity to the uPNP Server, or it can take a long time to retrieve song lists ... I've upgraded to TwonkyServer version 7.2.7 and still have the issue sadly.

Any similar experiences? Carl