I'm member of Insider Program. I'm getting pop up while starting window 'Update your windows before 15 Sep 2022'. And whenever I'm updating my window after restarting its showing 'Undoing Changes made to your computer'.
I got connected with Microsoft Tech team too, they tried their level best and suggested me to contact with you guys.
My apologies for the poor direction you received. Forum support for the Windows Insider Program is actually offered on a different site, found here. Nobody there will be able to access the notes from your prior support experience, but they are pretty good at digging into problems with Insider builds and fixing them.
Worst case scenario, revert back to the public release and wait to re-install the Insider build until an update comes out that may fix the rather odd issue you are facing.