I've owned my Nucleus for around 6 years and there was one stretch of a few months when it would seriously lag for 5 minutes before changing songs, sometimes not play, etc. Communication with Roon is not easy other than the forum. Their forums remind me of the chat forums from the 1990's.
See if there is a new software update. I'm not exactly sure how it got solved but it's been flawless again for years. Likely a software operating glitch. It can be frustrating to drop 2 grand and not be able to get a person on the phone. Prior to buying I suggest looking at their support methods to see if they work for you. I'm sure they work for most.