you could just try to set domElementAttachment="parent" at modal panel in order to prevent it's repositioning to body. That should fix the issue. But in that case you need to check that modal panel will works correctly at the page (reattachment done in general in order to avoid possible problems with relatively positioned elements which lies upper in DOM tree). If no visual problems appears in your case - that would be best solution.
Thanks, at a first look that did the trick.