I do remember from time to time seeing some documents that have elements with borders (and maybe blurs?) exhibiting rendering problems that you describe. You may want to try unchecking Use WebKit graphics acceleration and/or checking Position with CSS left/top in the Document Inspector and see if that makes a difference.
If not I’d be curious to see your project (zip of the .hype document) and the video you made. It’d also be useful to know what graphics card and OS you have.