https://ask.clojure.org/index.php/14788/threading-macro-with-update-when-produces-incorrect-results
See https://clojurians.slack.com/archives/C060SFCPR/p1764335092040609 which was the post here that led to that Ask.
I added the comment made on the thread here to the 'ask' post. Still in need of an explicit example.