As mentioned by others, this may be the 2 different readouts which become visible on the displayed image. The preview displayed is most probably not corrected for this (or not as perfectly as it is in Phocus), as it is not corrected for other issues corrected in SW. This is to make the preview faster to appear on the display.
Just what I believe, though.
hi, and sorry, i was away for a few days.
no, the image is ok in phocus. it was only that way on the display. (thats why i am actually not worried, but still like to know)
i have had the cam for three weeks only and will keep observing.