We have MX67W and one of the SSID's SSID1 in specific stooped working (No one can see it) and the only solution after all the troubleshooting is to move the same config to SSID4 !!!
Tried to change the SSID1 name to test and still no luck and we cant see it
After a week same thing happened to SSID4 and moved the config again to SSID1
Not sure if you have same issue