I saw someone posting about this in the timeline the other day, and I assumed that there may be something wrong with their blog content. But now I’m starting to see intermittent issues where my blog will fail to build because of some post, often quite old (in this case 2023-02-25 12:35:59: Error: Error building site: "/jsonbecker_b541ec/content/2013/11/18/more-evidence-for.md:2:1": failed to unmarshal YAML: yaml: line 1: did not find expected key) on a front matter issue. I have viewed this post in MarsEdit and on the web and everything looks good.
My clue that this is something similar is that the past person mentioned that " in the title appeared related to the issue, and sure enough, my blog post is titled, More evidence for "mere facts". I have tried changing this to More evidence for ”mere facts” to get things built, but this does appear to be a regression.