I first grouped them in BluOS, but I could ungroup them in neither place. Then I grouped them in Roon and I had a similar issue. I think you’re right, since then I haven’t had any issues. I subscribed to Roon now and I’m loving it.
My music files are on QNAP Drive, not the ideal as it the 251+, but I expanded the memory to 8GB. Roon core is on SSD Drive attached to the NAS Drive. My network is all WiFi, expect for the NAS Drive, which is wired directly to the router. That gives my problems only when using heavy DSD128 files. I have a Node 2, a couple of Pulse Flex, Pulse Mini. Then I also use my iPhone, iPad or Macbook Pro with a xDSD iFi DAC.
The only remaining question is related to MQA unfolding. I have a Node 2 is connected to an Integra DRX-X1. Node 2 unfolds MQA, but the Integra DACs doesn’t, although I need to check if the new firmware already do.