These builds and Dell laptops don't like each other :-(
Old laptop run Installing - 35% and then Settings app crashed. When I reopen Settings / Update there as announcement that build 18975 is available and there was Download button, instead of Check for updates.
New laptop run full Installing - 100% and after first restart is did "Undoing changes".
When I get back to Settings / Update page there was that same announcement as old laptop show also with Download button
My test desktop 2, which I got updated with WU has been up and running with no problems for about 25 minutes. It is a Dell. Test desktop 3 is updating with an ISO and it's a Dell also. I haven't seen any problems so far.