Yup this is a common problem as I've seen it all too frequently in the past couple of months, and throughout Windows 10's update history. Could be anything from an incompatible device driver to your dog being sick. Might have to hire Inspector Clouseau as trying to figure out what the problem actually is can be very daunting... One day Microsoft will design a "smart" PC but at this point and time they haven't.
All I can suggest is "if at first you don't succeed, try, try again"... Be forewarned though, at some point this could incapacitate your PC (no longer boots into Windows).
Thank you Elky64. I´ve tried so many times and I keep on trying but to be honest, I don´t see any success forthcoming. If you happen to see a solution or two somewhere please don´t forget me. I have seen some others with the same identical problem as mine, but I haven´t seen any solution. My PC is slowing down, I can´t install updates to other apps, nor can I reinstall anything until I can get Win 10 updated. Thanks again.