Pinacop theme problem

I purchased a copy of PInacop theme, but have discovered a problem with the header and header image on pages in that when header is activated and an image is installed the pages flicker when you try to scroll down.

The problem is resolved when no header images are activated, but the footer then appears half-way down the page. Could the author of this theme please explain?

Thanks

Rick

Here’s the support page for the Pinacop theme by @GPTheme