Hi, Pielit.
It was mounted on the side window, unobstructed line of sight 3 feet away. Experimented with it many days on the bench where it is within a foot of the computer, my phone, and the iFly. Over the course of a year or so, I have reimaged three different cards so many times I lost count. I've used version 1.5 and 1.6 software files, using the latest when a new one comes out.
The Crewdog guys had it for a few days, and could not solve it either. I assume a new Raspberry Pi board would fix it. However, for me, that is all in the past now, to stay.
Anyway, thanks for offering ideas,
Gary