Strange ND5XS behaviour

My ND5XS is playing up and I don’t know why. 

I control it via nstream app on my ipod touch and music is streamed from Synology NAS via Logitech Media Server.  When I try to play anything I am getting a ‘connecting’ message but mostly nothing happens.  Sometimes I can select a song but it takes me back to UPnP inputs selection. Sometimes I can select an album and then select a song, but once playing many functions stop i.e. pause, next etc (volume and mute still work). Sometimes the song will play after 4 to 5 minutes of ‘connecting’. I also experience the same problems using supplied naim remote control.

I have checked my Synology server which is working well and I can still stream music normally to my squeezebox players via Logitech Media Server.  I have tried turning everything off and on.  I have deleted and reinstalled nstream app but same symptoms. I think it’s buggered!

Everything has been working well for many months but I fear a software glitch with the ND5XS.  Am I able to do a factory reset? If so how?

Any suggestions as usual welcome, before I contact my dealer.