When I just got the 1809 update the other day, it was what messed up Windows Defender. I had LOTS of issues with WD after the update to the point it would not start, lag, freeze, not load and all kinds of weird things.
I also had a LOT of other issues with the computer, i.e., the time zone, date/time format, brightness icon removed from the battery, certain missing files, other changed options, Admin permissions being blocked when trying to move files... that had me in a fit!
I had not used WR anywhere near this update.
I tried to use WR AFTER the update and could not get the Safe Mode w/networking to work.
Instead, I had saved everything to an external HDD and reinstalled ver. 1809 a total of 3 times and it finally worked itself out, except for the Admin rights-very strange, but I think I have gotten past it (I hope?).
I am interested in trying the new 4.4.1 version, now that I have Win 1809 working but I am still reinstalling a few other programs that I need first.
So far, the computer is working great, now...almost better. lol
On the other hand, I helped another friend around the same time, over the phone, get their installation going and they also have an older machine and their 1809 update went on without a hitch-go figure! My guess? They probably don't change much to their computer so MS knew what to do, so to speak.