I am afraid that the Naim SuperUniti, when used as DLNA renderer, is just broken. I have tried *many* DLNA softwares, pushing music to the Naim, and it has never worked correctly, some times playing tracks twice, sometimes just stopping. And I have got somewhere on the Naim forum (do not remember the exact topic) confirmation that the Uniti behaves not so well when pushing music to it.
I eventually got what seems to be THE ultimate solution for me: BubbleUPnP Server running on the server, and Bubble DS on the (Android) control point. BubbleUPnP server (runs under Windows/MacOS/Linux) implements a standard called OpenHome, which seems to be built over DLNA, and to fix some of it flaws. It runs in association with/over a DLNA server (JRiver MC fits perfectly).
As control point (seems that there are not so many implementations), I use BubbleDS under Android. BubbleDS has an interface that is very similar to Bubble UPnP.
All the stuff is working perfectly for me for more that one year now. After I have struggled during two years to get the combination MC/Naim to work, this is just magic. Last but not least, once the playback has begun, on can put the control point (the Android tablet) onto sleep: no need to keep it awake.
The server is free of charge, and the Android App has an evaluation version limited to 16 tracks in the playlist. But the paid version is definitively worth the money!
Hope this helps.
CM
P.-S. The Naim Unity works perfectly when one browses the server's music directly from the device (or through the Naim app), but the app's UI is clearly not as convenient as BubbleDS's one.