Thank you for the suggestion! And yes, I do think I have gotten weird errors for other posts when names are too long and/or different types of punctuation in the title.
I'm pretty sure for this post the image did render correctly when originally published - but then I messed a couple of yaml option in different places (trying to modify RSS feed) and pushed to git without noticing the image not rendering.
If I rename the post, won't that change the slug and the url? So if that is the solution, then the links up to the published blog post break?
Is it worth trying just deleting nearly everything except the .Rmd and re-rendering? If so, would you delete the corresponding folder under
_site as well and re-build?