Over the past 2 weeks, the 5ghz-1 band on my A20 router sporadically disappears / stops working. All devices on the band disconnect and cannot find it for several minues. The 2.4ghz and second 5ghz band are unaffected. I've tried manually changing the channel of the band, but it didn't help. All the band lights, including 5ghz-1 remain lit & blue on the front of the router while this is happening. Any ideas?