Yes, I was testing the device indoors, with it sitting on an upstairs window ledge and was having the same problem, just with a weaker signal.
After speaking to a knowledgeable person, I was told that B20 is used for connections at the outer edge of the range. I have slowly moved up the bands and getting a stable connection when I manually lock it on B3. Why does the router not do this automatically? ie have a balance between throughput and stability?
Also, how can I locate the mast? If I pointed a directional antenna directly at the mast I could probably get it to be stable on B1.