A cache-overriding reload isn't a fix-all, but it is the first thing I tell anyone to try ("Hold Shift and click the Refresh button") when they're having a problem with a web site.

If the browser’s back button is not reloading the page, it might be a problem with JavaScript. The back button does not reload the page and that means that you can’t go back to the previously loaded ...

However, when you press the "Refresh" button, ... (and having a sandboxed iframe without allow-top-navigation results in an ugly message "Unsafe JavaScript attempt to initiate navigation for frame ...