I've had the same issue and fly for a television show full time. Out of 100 approximately flights this season about 25 had this problem bad enough to make the video link barely usable, and just pointing the camera in the general direction and hoping for the best produced just enough luck to keep me employed. So well motivated by that, I did some extensive testing and this is what I came up with...
As I believe it is a bug in go4 that causes more heat than normal in "l" devices, I took care of the more technical things first, like dumbing down the iPad so absolutely no other applications were running in the background, (there are a lot of settings that keep things running in the background, and it takes a long time, so just selecting a couple of off switches is far from making it as docile as possible, a few big ones I listed here ) no Wi-Fi, airplane mode, no video cache, and depending where I am operating, selecting the best RF band/channel for good measure. Even though I've tested that particular option extensively, sometimes auto is the most appropriate. Your mileage may vary as they say.
I operate mostly in Southern California, but travel to other states as the Shoot schedule dictates, but we are in the middle of a particularly hot summer right now, and I get maybe 1 flight before it's unusable, so my absolutely low-tech solution was just to deny the iPads the heat they seem to want.
I borrowed my daughters insulated lunch bag with an ice brick, and while keeping the iPads in their cases, and wrapped in a plastic bag to help avoid condensation brought them
out just before the flight, and returned them when we moved between set-ups. The result, crisp clean video.
Hope this helps, I look forward to any other solutions or suggestions anyone might have.
Cheers,
Joe
