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never updated to version 1809
Please, download the setupdiag.exe (https://docs.microsoft.com/en-us/windows/deployment/upgrade/setupdiag) . Run the tool and analyze the log generated on the equipment you haven't migrated.
If you have any USB storage devices plugged in at the time of the process, the reported error may occur.
(https://support.microsoft.com/en-us/help/4500988/windows-update-hold-for-windows-10)
Workaround
To work around this problem, remove all external media, such as USB devices, SD cards, and UFS cards, from your computer. Then, restart installation of the Windows 10, version 1903 feature update. The update should now proceed normally. If you are using installation media (USB flash drive, DVD, or ISO file) to install Windows 10, copy the files on the installation media to your local drive, and then start the installation from the local drive.