Was suffering this until today when I suddenly figured out what was going on. My iPad has login info for both 2.4 and 5ghz networks in my house. For whatever reason it'd sometimes switch between them and I'd get the connecting popup. Wasn't dropping signal from what I could see, maybe one was giving a better signal than the other and it auto switched or something. Anyway, removed login for the 2.4ghz network and it's been perfect ever since. Might help someone.