Default [Q] Wifi authentication failure at 2.4 MHz

Hello,

I have since the update to 4.2 problems with Wifi. The routers are found, after entering the password to an authentication failure occurs. Now I have noticed that it is routers with all 2.4 GHz. At home I have 5 GHz since everything is OK. I have already tried different ROM's and Baseband's, but no improvement. Since I have also flashed original 4.3, I now have Knox and can no longer be 4.2 or 4.1 flash, to taste.
Perhaps here one help, what can I do?

Greeting Ingo