I don't recall the previous postings on the Combo Update failure to install. Did anyone ever find a solution? e.g. just keep trying until it works? Download a fresh version of the DMG?
I don't recall anyone ever posting a solution, I've tried more than once on any number of occasions, even going so far as to d/l a new .dmg, but with no joy.
It may just be time for you to try re-installing Mojave. Can't hurt...may help.
