There is an issue here when I checked, in that the latest episode appears in the web page version of the iTunes Store but not in the Store within iTunes. Then when I checked again the latest episode appeared, so I assume it is as described coming and going. Currently two of the podcasts seem OK but Myth vs Craft isn't showing the latest episode in the Store in iTunes.
We've had odd problems with the Store before, usually in the form of claiming to show a given number of episodes but showing fewer or none, though this stopped some time back. This is a different issue, but I can only conclude that there is another glitch happening in the Store.
The good news is that this does not affect subscribers, who will see the latest episode as son as their iTunes application checks the feed. The bad news is that I have no way of knowing what is going on. If it continues you could try contacting Support: Go to https://itunespodcasts.zendesk.com/hc/en-us/requests/new and click the disclosure triangle at the right of the 'Choose a topic' field - choose 'Other' and proceed from there.