I have a similar periodic problem, where either it keeps popping out of focus, so I touch the screen and it goes into focus then 5 secs later it goes out of focus, yet everything in the scene is at least 200 m distant. Last weekend during mid-flight it just wouldn't focus even when I tapped the screen. After about 5 mins it did focus, but I missed some good footage of a sailing race. :-( I'm amazed it can go so much out of focus as surely the 95% of the time the focus would be at 'infinity' and rarely less than about 5 metres.