The basic issue is that the way content is pulled from your site is that it uses a gem called Readability which is based on the Mozilla reader view algorithm.
Essentially what is happening here is that the readability algorithm doesn’t play nicely with image-heavy content. The preview feature is intended for posts that are mostly text.
Basically, yes. One way to test is to use the reader view in Firefox with your Wordpress post to see what the readability gem is likely to produce.