Wifi passphrase keeps changing to default and internet signal constantly dropping signal

My passphrase in the Wifi setup keeps changing back to default at least twice a day.  I change the passphrase and hit the apply button.  I made sure it was changed on screen, even logged in on my devices.  Then a few hours later, it will automatically change back to default password.  Also, wifi signal drops constantly, at least every other hour.  Any help would be greatly appreciated as I am ready to throw the thing out the window