I have experienced this with all my quads but I really would like to know specially about the I1. Last night I was to fly it 4200 feet. It started have "weak remote signal" at 1600 feet but I would stop gain a bit more height and signal would come back and I would continue on. I was able to get out to 4200 feet but today I couldn't get past 2100 feet. Solar activity etc looked ok today. Anyone have experience with this?