Static homepage template won't let me select "latest"

I’m trying to create a page as the “latest comic” entry point. This should be as easy as creating a static page at the URL I want, and selecting “Latest” from the dropdown at

Webcomic Homepage > “Show the [] webcomic”

However, it won’t stick–it always reverts immediately back to “First” after I save changes to the Page, and that’s what the generated page has on it.

Any idea what might be causing this? A workaround?