But the NDX keeps losing its connection / I can’t use the app and I have to reboot it. It would continue to stream radio once connected, but I can’t connect using the app.
Have you swapped ND5 and NDX connections to determime is you have a cable connection problem.
Next I suspect a possible router error / corrupt link.
First clear the control point (tablet or s.phone) cache - force it off & restart
Then turn everything off, including router & wait at least 5 mins to be sure the ISP logs your’re off line.
Start router only and let it finish its restart sequence
Start NDX
Start control point … and test for the problem
The NDX is same era as the NDS, my NDS suffered the same until I uploaded and use the latest Naim app. Also ensure the firmware of the NDX is 4.8. (Before you start using the latest app switch off your router and have it reboot)