Have you tried changing settings on the 2.4 GHz band - Prodessional - there is
a setting for just this problem : I am not at home and can not remember what it is but it is a setting there you can change from no to yes. Look in the forum
here where other users had had the same problem.
Update found it : Add enhanced interference management option for 2.4GHz in Advanced settings->wireless-> Professional
Originally Posted by theviper04
I have an rt-ac66u and it keeps dropping 2.4ghz signal, the 5ghz signal is flawless and it keeps dropping so I have to restart the router every once in a while. I originally had it at the latest firmware and then I upgraded to the asuswrtmerlin latest one, that didn't work either, I didn't expect it to anyways. This was my replacement for the 1st rt-ac66u I had which had the same exact problems, constantly dropping 2.4ghz signal. Its a rare thing to receive two lemons so I think its a software issue or something else.