Does my AC1750 / R6400v2 Router need to be replaced?

[opticomm]

My router is a Netgear AC 1750 R6400v2 802.11ac Dual Band. My 5.0 Wifi generally runs better in our small (1500 sq ft) home, but every so often it reverts to 2.4, then a weaker signal which causes my system to slow down significantly. So I switch back to 5.0 and everything is fine again. Is this somehow the fault of my router, i.e might it need to be replaced? Or is there a fix?

[FURRYe38]

What reverts back to 2.4Ghz? 

IT's up to devices to pick and choose where they connect too. 

[plemans]

do you have your 2.4ghz and 5ghz band named the same? 

If they're they same, change the ssid's on the 2 names.

Then delete the 2.4ghz from your phone/devices remembered devices so it doesn't switch to it. 

[opticomm]

It happens on almost any device I happen to be on but mostly on my iMac, my wife's Mac, and my HP printer, and all are within 8 feet of the router. My Smart thermostat, which works only on 2.4, just loses its connection every few days and usually when I reboot the router (pull the power plug for 30 seconds and replace) it will come back on. Every so often the TV will switch over to 2.4 and becomes useless.until I get it back to 5.0.

[opticomm]

Each network has a different name.

[plemans]

If they've got different names, you should be able to go into your devices and "forget" the 2.4ghz ssid.