I took a really quick look into why this might be and I think I might know.
In the original Squarespace the images had + in them as a part of the filename. However, now when looking at the source code that has been removed and presumably broke the image source links.
Please see the attached examples taken from the original Google Docs file
Blog Issues.pdf
I took a really quick look into why this might be and I think I might know.
In the original Squarespace the images had
+in them as a part of the filename. However, now when looking at the source code that has been removed and presumably broke the image source links.As a concrete example on the original post https://www.evidenceaction.org/blog-full/reflections-from-winning-start-volunteers there is an image on the page https://static1.squarespace.com/static/546f9316e4b0ced8102e4c74/t/5bfec5c0758d46d2e74172ea/1543432153408/Marion+Jeptoo.jpeg
However on the Wordpress one I see the same image referenced as http://evidenceaction.org/wp-content/uploads/2018/11/MarionJeptoo.jpeg which results in a 404 error.