The dffsRedir=1 is applied to the redirect url so if you see that the redirect has been done. Try opening the developer tools in the browser (hit F12 > Open DevTools (if prompted) > Select the Console tab) and look for errors when you try to save an item.
You can also turn on debugging on all presave actions by checking the “Activate debug on all presave actions” in the top of the Rules tab to see if it does what you think it does.
Alexander