The others just failed with random hexadecimal error codes, again I had to Google to try and work out what was going on.
With one of them I had to use the command line and diskpart etc. to expand the recovery partition because apparently the default size when I'd made that Windows 10 install was no longer big enough, and Windows Update couldn't work this out (the error code from the failure was nondescript, took ages to find out what was actually wrong) and couldn't fix it. Had to do it manually in Powershell.
Another one I think might have fixed by running sfc and dism recovery commands in the command line, again it would be nice if Windows could work this out itself!