Well i solved it i installed stock firmware latest then used "http://192.168.1.1/Advanced_Wireless_Content.asp"
From there i set my channel to 149 that's it no more disappearing 5ghz band boom hope it help somebody else
Hi i just recently installed merlin latest for ac66u i am using repeater mode of my router 2.4ghz is repeating my network i understand both router needs to be on same channel for repeater mode but 5ghz channel i want to change as my device's support only channels that are above 140 while in...