Dual Band Broadcasting / Only 1 Works At A Time

I'm trying to save a neighbor some money by fixing their wireless network.WNDR3700 Dual band Netgear router.2.4ghz wireless b/g/n with enabled SSID broadcast, channel= auto, mode set to 130Mbps WPA-TKIP + WPA2-AES. wireless isolation is not enabled.5Ghz wireless a/n enabled SSID broadcast, channel = 44, Mode is up to 300Mbps..No security encription. (i know...bad, but the lady has lots of kids and family members coming and going from the house so she doesn't want one encripted). Video network enabled..Both Radio frequencies are enabled, fragment and CTS/RTS set to max WPS settings = keep existing. IPv6 not enabled, No repeating is enabled, No guest networks are enabled(however ssid broadcast is enabled for guest profile 1)The problem, and reason for fixing the problem is that the 2.4 Ghz band light on the router is ON however the SSID is not being seen by any client in the house. the netgear interface says it is on and working. the neighbor needs the 2.4ghz band to work because the printer is wireless and will only recognize 2.4Ghz SSIDs. Also they have older nintendo DS clients they would like to use on the network.During the day the 5 Ghz band works with very seldom (1-2) disconnects while the 2.4 Ghz band wont be visible to any device. in the evening both bands will come online, and very often will every computer get disconnected from either, the 5Ghz band will stay online longer than the 2.4 band and it seems as though every 10 minutes everyone gets disconnected from 1, and then all the sudden the other band will start working. once every so often both bands will be visable by all computers however only 1 will work.

-Updated the firmware, appeared to fix the problem. Fix only lasted for about 5 hours.
-turned off the router and modem to let them sit. restarted both multiple times.
-Called netgear tech support, asked me about firmware, restarting, then rerouted me someone with more broken English and a horrible phone connection than ive ever seen or heard. then they tried to charge me 30$ for a 1 time. or 100$ for the year. might as well buy a new router at this point in costs.

My personal fix would be to just broadcast on the 5ghz band and wire the printer to the router, buy another router and broadcast the 2.4 ghz one from it, but the lady wants it all to work with the one router. i dont know if the networked has ever worked as intended and ive spent hours reading forums.the main issue is leaving her with internet that she and her family can use so kids can do homework and stuff after i leave the house.