If it is only a few seconds then it is not the defrost cycle. My compressor would drop off for a split second intermittently and my voltage gauge showed excellent voltage at the campground. This was the 4th campground on a 3 week trip. Back home now and I ran it several day on my hookup and could not duplicate the problem. I have not yet checked for anything laying against the evaporator or loose connections. I do notice that the thermostat variance is 2-3 degrees which is not normal.
Haven't had time to dig into it any further.