Recently it always fails with a BSOD at around the 9% - 13% done on the "working on updates" phase. The BSOD stop code is usually "IRQL NOT LESS OR EQUAL" or "MEMORY MANAGEMENT".
To run the update I disconnect all external devices except internet, mouse & keyboard, I restart the PC, log in (each of my family have a login - mine is set as administrator) and then run the update by right-clicking on the MediaCreationTool22H2 icon on the desktop and selecting "Run as Administrator". I then follow the prompts i.e. select Upgrade this PC, accept licence agreement, click OK to install Win 10 Pro and keep files and settings, etc. The install reboots the PC once during the process prior to the installing Win 10 phase. Each update attempt takes around 90 minutes with most of that time taken up by the Win 10 download. During the update there are two checks for updates and also two checks to make sure the PC is ready to update - none of these produces any messages. All seems normal until the BSOD appears.
After the rollback to Win 7 I recall that the BSOD initially didn't appear until around 84% done in the "working on updates" phase.
After the initial successful install/registration of Win 10 (1703) and the subsequent rollback due to problems with Avast, the rollback resulted in a number of permission issues and settings changes i.e.
. All files had the lock symbol next to them in file explorer and some people could no longer open files that they could previously open. Even my admin login couldn't open some files but I could reset permission levels to default or add user Everyone which resolved the issue.
. Even though the default browser was set to Microsoft Edge, attempts to open url's resulted in a message to select a browser being displayed. Setting the default browser to Edge again (even though it was already set to Edge) resolved this issue.
. There were similar issues with other default apps already being set but which Windows was apparently ignoring until I "set" them again.
. Plus some other issues I can't recall at present.
Over time I have tried upgrading:
. from DVD, USB and using the Media Creation Tool for 22H2 from the desktop.
. without first rebooting the PC,
. without selecting "Run as Administrator".
. doing a disk & system files cleanup from the C:\ properties window by selecting all files before the upgrade,
. without disconnecting external devices.
. using Win 10 versions 1703, 21H2 & 22H2.
. after disconnecting the internet but the upgrade failed immediately as it couldn't find the internet to download Win 10.