Multiple users have seen issues where when 2 or more Naim devices are in the same Roon multi-room group, the sound synchronization between the devices drifts over time. See this thread in the Roon forums for more details.
All reports, so far, have the Muso 2 as part of the setup, so that may be the root cause.
This problem is RAAT specific as two of the 3 reports (as of 1/6/2025) indicate that using the Focal/Naim multi-room functionality does not have this issue.