For the last year, my laptop has refused to install Win11 24H2. It would hang and revert in the background without installing. With Win11 25H2 available and also failing, I decided to finally fix this.
Sometimes there was an error code 0xC1900104 which means it timed out.
Searching around, there are suggestions to remove drivers, download the ISO to install instead, and do Windows Update repair.
I narrowed it down to the Sennheiser Audio driver by looking at setupacct.log in C:\$WINDOWS.~BT\Sources\Panther. That driver was listed as the last item before it hung and reverted.
After uninstalling the Sennheiser Audio driver, install proceeded as expected. And I've not added the driver back.
What's the odds I remember this a year from now when 26H2 is released?
UPDATE Sept 30, 2026:
In a delightful twist, Win11 26H2 installed today without having to do anything special. Perhaps the issue is fixed for future updates as well.