This can be reproduced quite easily.
1) Set up a router with *SSID. Test that it connects fine. Reboot the modem. Notice that it retains the router setting.
2) On this same modem, set up the SAME router it has currently stored using *NS. Test that it connects fine. Reboot the modem. Notice that it does not retain the router setting.
(In #2, you can set up a different SSID/router but using the same removes one variable for testing puposes.)
1) Set up a router with *SSID. Test that it connects fine. Reboot the modem. Notice that it retains the router setting.
2) On this same modem, set up the SAME router it has currently stored using *NS. Test that it connects fine. Reboot the modem. Notice that it does not retain the router setting.
(In #2, you can set up a different SSID/router but using the same removes one variable for testing puposes.)

