I dealt with a machine a few weeks ago that was stuck on 1803, and would bluescreen when going through Windows Update to 1903.
I used Rufus to download and create a 1809 USB, and used it to installed 1809 OK.
Then I did the same with a 1903 USB and a 1909 USB. That was the only way to get that machine updated, but hey it's on 1909 and it seems to be working fine.
More details:
https://pureinfotech.com/download-older-iso-windows-10/
Rufus homepage:
https://rufus.ie/
edit: oh you already got it to update ok. Nice, good luck with the rest of the updates.