And 19043.928 is the one and only 21H1 build now offered to customers on Techbench and by the official MCT. And as long as it is 19043.xxx it doesn't matter, the xxx part is by cumulative updates, pre-release doesn't mean the same as in the past since 1903>1909 and 20H1>2>21H1.
In conclusion (maybe I'm wrong), but I believe that the "triggers" indicated below are responsible for WU repeating the download of LCU's, in system images built with these updates already previously: Microsoft Edge package removed in slipstreamed W10 images; Microsoft-Windows-Client-Desktop-Required-Package; (this, I confess that I do not know what it is...) Windows-Foundation-Package (.NET Framework); LanguageFeaturesOnDemand; Windows Update Delivery Optimization (WUDO).
Display /monitor size increase is one of the major reasons for that matter, I used XP back then in 14" CRT monitor, now I use 42" 4K monitor with 4k rezd wallpaper, & that img MSFT shared for old XP default wallpaper, is in FHD rez.
All new updates July 13. 2021: https://forums.mydigitallife.net/threads/windows-10-hotfix-repository.57050/page-641#post-1674572
I am getting this error everytime, I have tried many times, but still getting this error I am currently on version 19043.1055
Updated the 20H1/2 / 21H1 Updates Overview: https://forums.mydigitallife.net/th...-2-21h1-vb_release.80763/page-16#post-1571109
@ashish1989 grab the latest available build from uupdump, mount the iso, start setup.exe and perform an in-place upgrade. You can preserve all your current programs/settings/etc.
One trick I have had to use a few times is to combine the image you currently have with the update you want to install. Use UUP dump to grab the build you are currently on and then use W10UI to integrate the current CU. Do not use the cleanup option on UUP or W10UI. Doing an in place upgrade with the resulting image has had a very high success rate for cases where all other attempts to upgrade have failed. I had to do this with a suborn system yesterday. WU was reporting success and then on reboot the update would fail and revert. Attempting to go directly to the new build through UUP also failed on reboot reverting the update. I was stuck on 19043.1082 (19043.1083 was also failing) so I downloaded 19043.1082 from UUP (no cleanup) and then integrated KB5004237 via W10UI (also no cleanup). The resulting image was able to upgrade that problem system to 19043.1110 without issue. I believe that starting with your current build and adding the latest build combines replacing missing components preventing the upgrade with the actual upgrade in 1 step.