Intermittent loss of U-Verse signal

We have gigabit fiber with telephone and U-verse TV. Phone and internet work great but we are plagued with intermittent loss of U-Verse signal while watching TV. Once it starts it happens about every six minutes and is out for abou t 2 minutes then resumes for another six minutes. Restarting the gateway breaks the cycle for several hours but then is starts again. My wife has found that if she switches to an adjacent channel then back the picture resumes immediately but on anything recorded during the behavior there are two minute gaps every six minutes. Restarting the set top box seems to have no effect on the phenomenon. Any suggestions?