Mixed BluOS playlist problem

I'm new to the BluOS system but am enjoying the flexibility and software. However I have a problem which seems to my mind be a software issue. I'm using a Bluesound 131Node via USB into a Cyrus pre2 QXR DAC.

I have created mixed playlists with tracks from my (updated) Synology NAS and Qobuz. Going from Qobuz to NAS everything plays fine (most tracks on the NAS are ALAC 16 bit 44.1Khz) but going from NAS back to Qobuz I get a burst of white noise then the DAC shows no signal from the Node and play stops. If I disconnect the USB cable and reconnect it all plays fine. The DAC is just playing a PCM stream so I'm a bit mystified as to what is causing the problem.

Any advice or help would be appreciated

Graham