Blog post preview not working

Steps to replicate:
Start composing a blog post, add a title, few content
Click the drop-up arrow near save, hit preview. The page which opens up, shows a 404 error.
You may try this out on your demo website, check up the screencast https://www.youtube.com/watch?v=t1uNU3TW8f0 (From 1.55 to 2.25) {x.yy format, where x is minute and yy is second}