We are having an issue with the preview post feature recently.
When creating a new post and clicking on the "Preview Post" link we either get an old post that was published before or we get a 404 page.
The 404 page issue is happening because for some reason the url has 2 extra characters added (&). Removing them in the url allows us to see the previewed post. Not sure why that happens.
The newest issue however is just showing us an old post instead of the new post we have just created.