I have also noticed this. And it happens any time that you have done anything that will cause a page or screen update. So both on navigation and Save or Delete. While the delay is occurring, you will see or at least I see with Firefox and WIN 10 some moving grey blocks over and just below the main tool bar at Top Of Screen, particularly at the right end of the bar. I mention this only to say that it is an indicator that the browser is waiting for a response from the server, and not that your browser is hung up. I will add that 10 or 15 seconds delay seems to be what I am seeing, and not 3 to 4 minutes.