An unusual one today: whilst playing vinyl records, using the NDX 2 to switch to the Phono input on my NAC-282, I noticed after a while that the NDX 2 had taken itself into setup mode. It asked to pair the remote, set the language and then tried to connect to wifi, which it was unable to do.
The Naim app was behaving in a similar fashion, going through the setup sequence until it reached the stage where it checks for a firmware update (I am already running 3.5), whereupon it just kept searching. Restarting the app only started the whole setup sequence again on both the app and the NDX 2.
In the end I resorted to a hard reset on the NDX 2. It then started up normally, so hopefully this is just a momentary glitch, but an unusual one.