Images in scroller not displayed

Not sure why but sometimes the images in the scroller are just not displayed. And just as they vanished from sitgth they reapear. The images on the product are visible and the images are located on the server.

Not really sure what causes this behaviour. Scroller is set to display the newest items of the past 30 days. It seems when new products are added the scroller gets confused and does not display any images. Clear cache does not help.

Any one else noticed this strange behaviour? Any advice is welcome.