I have been flying a year now and onto my fourth drone, a Mavic Pro which had its second flight today. I still have a Spark which I flew for many months till it fell out of the sky. In the early days with the Spark, I was frustrated by problems with transmission, lag and pixelation. I kept thinking it was the Samsung phone which I was using. It was actually a low-end model and someone suggested it might not have enough processing power so I tried my Sony Xperia and surprise... the problems went away. So I bought a Samsung Tab and it worked well until that frightening glitch.
Then with the Mavic Pro, I had signal and image loss problems on the first day. I kept thinking it was the drone or controller but then someone in Australia said that it was mostly likely that the processor in the tablet was not powerful enough to handle the latest GO4 app. I tested the idea with my Xperia again and it seemed true because I had no signal loss on takeoff. So I had confidence to buy yet another new tablet (a Huawei MediaPad M3 which many people found to be problem-free) and on today's flights, it worked perfectly with the RC.
So for those who have connectivity problems, I would suggest you think about the device you use and check its specs. GO4 is getting more complex and needs devices with more processing power and speed. Don't rant and rave at customer support (and even louder when they say there hardware has no problems) until you have exhausted all other possibilities.