Platform Theme – Content Is Moving Background Image

I can’t get my image to stay aligned at the top of my page. Everytime I add content to a page, the background image moves further down the page.

Here is a page with no content, with the image where it should be Here

And here is an example of a page with content where the image has moved Here

Any he;p would be greatly appreciated as I can’t find ANY on this subject in the forums!