I have now had exactly the same problem with two computers and in both cases have had to roll back from 1903 to the previous version. I stupidly assumed that, since the first time this happened was months ago on a different computer, that Microsoft would have fixed the bug.
(To explain: the update created a new user with .000 at the end and put everything from the proper user's folder there. The result was that Outlook did not work (because it was looking in the wrong place for the .pst file) and it couldn't access Onedrive. I did not stop to find other lost functionality before rolling back.)
I am not a superuser and don't want a "try this, it might work" kind of solution. I want Microsoft to fix it.