Does anyone know under what conditions a dynamic route that has been prefetched with router.prefetch will be fetched again when navigating to it?

When I do a simple test with a fresh create-next-app, I see the expected behavior: if I call router.prefetch(href) followed by a navigation to href, I only see one fetch request to the server for the route.

However, in my application I am seeing a separate fetch request made on navigation. I am trying to isolate what's different between the two, and looking for any pointers (e.g. middleware, the use of dynamic functions, parallel routes, etc).