thank you Csaba for looking into it.
http://i.imgur.com/fKfB1Jk.jpg - loaded correctly
http://i.imgur.com/USU6WBB.jpg - loaded incorectly
Can be reproduced by loading homepage then scrolling down into the content area before the other images have loaded.
Then scroll back up after 5 mins after all image slides have loaded. My image slides load every 16,000 secs x4 slides. initial slide image will be ok, but all subsequently loaded will not be.
it is unrelated to my plugins as have disabled them previously.
I have read some old posts where this was previously documented as a bug.
I believe it is a flaw in the way the parallax effect is made to happen. as the new loaded image is positioned center of where your screen position at the time of loading. i tried restricting max-height of 100% for “slideshow” “header-slider” “slide-item” but did not work for me. maybe worth trying the container also.