Tried flashing both alpha versions available for my RT-AC68U v4
(RT-AC68U_386.7_alpha1-g82406ddc5d.trx and RT-AC68U_386.7_alpha1-g8ee6420ea6.trx)
to see if this would fix the issue with my 2.4ghz network becomes inoperable after a period of time. Seems others have reported this fix this issue...
