I wouldn't say that this is a BLE/radio issue. I could advertise (and we have tried this) every 20ms and the app might still do nothing at all. As soon as I light up the screen of the phone, then the app will connect. The problem as we see it is that the phone stops scanning/pauses scanning/something similar in the background in a different way than previous OS versions did. And I'm curious to find out if there is any documentation on those changes and potential fixes to them.