Hello,
Recently Windows 10 has forced a couple of updates on me that in my humble opinion was responsible for NoMachine dropped connections. The symptoms I had was for (NoMachine mobile to Windows and NoMachine Windows to Windows) dropping connections and attempting to reconnect over and over, never obtaining a stable connection no matter what NoMachine settings I had used. After nearly pulling my hair out I resorted to an obscure fix I found on the internet to Ensure that SMB 1.0 is manually enabled.
Once I went to Control Panel > Programs & Features > Turn Windows features on or off and enabled the SMB it fixed all my connectivity and stability issues for NoMachine. I am back up and running again with NoMachine and am very happy with the latest release 6.8.1.
Hope this helps others out there having these dropped connections.