400 Bad Request from AEM-SPA-Model-Manager

The AEM SPA Model manager is initializing correctly on my page. I provide the page path and it successfully retrieves mypage.model.json as a 200. But then it starts looking for literally ".model.json" and it gets a 400 response

What is happening? I have AEM running on 4502 and react running on 3000. It was working previously and now inexplicably has started getting these 400s