Odd to come across this issue (which has been troublesome for me) here of all places!
#1 KB5004237 isn't the optional update - but it failed on one of my machines and there is a lot of evidence online that it has been troublesome for many.
#2 The optional package failed on the same machine...but my money is on KB5004237 being the root cause as it failed first and predated the optional one.
#3 Ironically the machine that isnt taking the updates is very new and has the fewest and least complex apps installed -a Dell XPS13 9310. I'm hoping that this months main 'roll-up' update will fix the problem - otherwise it'll be back to a fresh install