Easy Slider

Dear all,
On the easy slider I got an issue which I can’t figure out.
I got a couple of images included in the easy slider. Now this easy slider is all jumpy.
I would like to have my settings like to first slider being shown (Mont Ventoux)
Now I did inspect the image at the front end and noticed the following;
span.image-overlay.overlay-type-extern

Maybe this is not the issue, but how can I make sure that the image will not be all jumpy?

Thanks.

For your reference please see;