About once a month on my 2013 MacBook Pro I get a message appear saying "Time Machine couldn't complete the back up to my Time Capsule". It says a network problem interrupted the back up, telling me to check things and try again. It also tells me that last successful Back Up was some time ago, that could be anything from a couple of months to a couple of years. Now I know nothing much about the Back Up system because I rarely use it, but am concerned if it is not working properly. I do know that on a very regular basis , hourly I think, the Time Machine icon if clicked will show the various stages of Back up occurring . Could someone please tell what is going on and how I can tell if my Back Ups are actually happening correctly.