I checked using wifi analyzer tool and the 5GHz connections bandwith is 80MHz.
The mode also already set to 11 a/n/ac mixed.
My router support 5GHz mode on channels : 30, 40, 44, 48, 149, 153, 157, 161, 165.
I have already tried channel 149 - 165 with the same problem.
But something strange is...