The focus point on my Pen F shifts on a very frequent (and very annoying) basis. I set the green focus square in the centre of the grid but in no time it shifts seemingly randomly to a different position. I am traveling at present and taking lots of photos and have mucked up or missed a number of shots because of this. The camera is set to S-AF. In the menu I have gone to the AF/MF menu and gone to 'Set Home" (ie choose the home position of the AF target) but nothing seems to help. There is probably something simple I am missing so hoping someone can help. I just want the green square target point to remain in the centre all the time, unless I choose otherwise!