+++ This bug was initially created as a clone of Bug #42940 +++ User history navigation (back/forward buttons) while there is network traffic does not always fire a popstate event. These events are completely lost, and can get an application into the wrong state, where the user navigated through their history, but the app was never notified. Seen in Safari 9.1 (11601.5.17.1) and Mobile Safari on iOS 9.3.2. Issue is not present on Chrome and Firefox.