No backup file used, total manual reconfiguration was applied. I coming back with any new developments on the issue.

Of course I used the default IP adress to access router. After 15-20 seconds the login window is visible with the new GUI. I have no idea what is happening. Previous FW upgrades caused no problem at...

No I did not make experiments like that. Btw, many thanks for this idea, next time I will try.

Region : Argentina Model : TL-WDR4300 Hardware Version : V1 Firmware Version : ISP : After upgrading the wifi signal become very unstable both on 2.5 and 5 GHz. Wifi signal disappears and reappears...