I have similar problem appearing ever since one of my neighbours brought a new wifi router. When that router is off everything returns to normal. It's annoying since I can't find ways to shield my tablet. I don't think it's due to too many APs since there are only 5 in my surrounding, and I had been in places with more than 30 APs that 770 works flawlessly

Does anyone know how to identify the brand and model of that router? That may help nailing down the problem.