3D FlipBook - Having an issue with some of the Flip Books displaying horizontal lines on some pages. At first, I thought it was due to the

Having an issue with some of the Flip Books displaying horizontal lines on some pages. At first, I thought it was due to the size of the PDF files but I have since optimized the versions being used in flipbooks. Of the optimized versions, some show the lines and others don’t.

No Lines – https://seefusslug.com/?p=708 Lines – https://seefusslug.com/?p=707

The lines do not seem to appear on every page. Is there something I need to do to the original PDF when saving or some way to modify theme/plugin CSS to prevent this?

PDFs are being hosted on Amazon S3 (Bucket CORS – updated) and I am inserting the Flip Books with URL from the Page/CPT because the create flip books doesn’t allow me to select URL instead of the media library.