Issue with background shifting in Avia Lightbox

If you click on the large image (see link in private content), it opens in lightbox, but you will notice a shift of the background also. Happens in Firefox, Chrome and IE.

I narrowed it down to the jquery.magnific-popup.js file:

if( mfp.st.fixedBgPos === false || (mfp.st.fixedBgPos === ‘auto’ && !mfp.fixedContentPos) ) {
mfp.bgOverlay.css({
height: _document.height(),
position: ‘absolute’
});

If I remove the “position: ‘absolute'”, the issue is resolved.

Thoughts? I was thinking it was something in my Quick css field, but when I remove those, it still occurs.