For 3-4 months I had no problems with the app's connection to the ND5SX and my NAS server (running Minimserver).
But since 1-2 months I once again suffer from the app loosing connection to the ND5SX , saying "No rooms found" when I close and restart the app. The problem is that the app doesn't find the ND5SX - with app and ND5XS connected it only rarely, if ever, has been a problem finding the NAS/Minimserver.
The drop of the connection can happen anytime, even while I'm using the app. Closing the app and restarting it doesn't help. Shutting down router does, I think, and pressing Pause and then Play on the physical remote usually does as well.
There has been no changes to my network in this period (from when it worked reliably 99+% of the time to now when I have connection problems regularly). The app however was auto updated to 5.9. (I think it was) just about when the instability started again.
I have mentioned this here before. I do hope that Naim will provide their customers/users with an app less sensitive to whatever it is that triggers the dropouts and prohibits reconnecting simply by restarting the app when it does fail.