CSRF shouldn't matter at all for page templates.
Seems rather like there is a bug in the page template edit page urls. After you save, all the urls become wrong. If you click on the breadcrumb of the template you created/edited/etc, the urls in the tab for "test" and other things are correct again.
Or you can just manually open up the template directly in another tab and test that way instead of having to click the "Test" button.