Ah, thanks.
I'm pretty sure I went thru the partition resize exercise earlier in the year. My recovery partition is 620MB.
When I just checked for updates now, WU says I'm up to date - no patches required.
But KB5034439 only shows as a failed install under the Update History list.
Oh well, have to see what happens next Patch Tuesday eh?
Thanks for you help to get this sorted.
What were your fixes actually changing on the server to allow WU to work?