Have you tried to manually apply the update for 1903 on a box that failed this "Service Pack"? My experience has been that 1903 is a major upgrade with lots of new security enhancements. I had to upgrade several pieces of applications because they were preventing the upgrade. SnagIt was one...
When you manually apply, they upgrade installer will let you know where it failed.
Yes i have manually run the same ISO on my machine this afternoon and i am now on 1903. I wont get into the things it has broken post-upgrade here though!!!
I am confident the ISO itself is ok and aside from the usual microsoft dialogs/next buttons before it starts the upgrade theres no showstoppers like antivirus that cause the setup process to abort abnormally (I have seen that on previous service packs but this one looks ok)
So in summary : Manual ISO install = OK - Deployment of same ISO via Client Management = FAIL
Could it be possible that the there was still a reboot missing? Could explain that it works a few hours later?!
Errorcode 1 doesn't indicate a very special error.
Before you run the updated, you could check the Windows event management.
You did not told us if this error occurs on all computers, on some or you this one.
Please make sure that the "SYSTEM" account is able and allowed to mount a ISO file.
Could you suggest a way i verify that? The local administrator account we use for the BCM agent has loaded previous service packs without any issue. Since it is a full admin i can't imagine there would be any issues here.
Are you saying i should try and run the ISO logged in as the BCM account ?