Sorry it took me a while to get back to the Nucleus - original case was (ref#IVPGQN) .
The extension mentioned previously is disabled. It was enabled on the Mac mini and caused no issues, however.
Note, BTW, that on the mini it’s quite clear that RoonAppliance is leaking ports; it was slowing down over time, and checking its memory (limited to 8GB) it was consuming over 140K Mach ports! A typical process is < 1000, and when started RA is about 500.