Thank you for reporting this bug.

The link has a video URL attached. Summit incorrectly assumes that posts with a video URL do not have other URLs which is an assumption that is false. I'll look into a fix for the next release.

Edit: oh actually this has to do with a property of posts. Posts can have a video attached to them. When I supported this field I didn't really understand what it was until now. It's similar to a thumbnail but it's a video instead.