Same issue...usually with formatting.
I think the problem is that a lot of editors (mine included) use previous versions of HTML or XHTML. The Auctiva editor strips and re-codes any non current HTML. Problem is, eBay doesn't care really...or at least has a better code engine.
I like using my old WYSIWYG editor but the Auctiva code engine tears it apart.
Work around: when listing, copy and paste your older code into the HTML side of the editor...not the standard side. NEVER go back to the standard editor. Finish your listing (shipping etc.) and SAVE. You can then preview your listing from the saved listings page. If you need to edit anything (the text or any part of your listing) you'll have to go to the HTML side of the editor again...delete everything and re-paste.
Another issue is that once listed there is no changing. If you go to edit inside eBay the formatting will get junked again and unless you want to wade through all your code there's no going back.
I also suspect the scrolling gallery script is not properly closed and it's formatting is bleeding through to the listing.
Just my thoughts...not up to speed on current HTML.