Can't edit latest version of UI mockup created for a Confluence page

I can't edit latest version of UI mockup created for a Confluence page. Please see the attached screenshots.

To replicate the problem:
1. Create a new page in Confluence or go to an existing page.
2. Click on the +Add icon at the top left and select Add UI Mockup.
3. Make changes to the UI Mockup and go to Mockup -> Save and Close.
4. On your page, a thumbnail of the UI mockup should appear with an "edit this mockup" link below it. Click the link.
5. Make additional changes to the UI Mockup and go to Mockup -> Save and Close.
6. A second image with an "edit this mockup" link below it will appear, but instead of a thumbnail, it will be a red X, as if the thumbnail were unavailable. The link will be the same as the first link: They will both go to v1 of your mockup, and you will not be able to access the latest version of your mockup.

When you look at the Wiki Markup view, you'll see that there are actually two versions, but ... how do you get to v2?

Thanks,
Charlie