Hello, I am struggling with upgrading my 1903 Windows release to the latest one for several months now. After several update tool versions I have finally dowloaded 21H1 ISO and started upgrading from it. Unfortunately again no luck. The problem pops up after second restart, and installer roll back changes with following status. 0xc1900101 - 0x20017 INSTALLATION FAILED IN THE SAFE_OS PHASE WITH AN ERROR DURING BOOT OPERATION I have disabled defender, do not have any other antivirus app installed, I have no other drivers apart Parallels ones.
Make sure you have over 10 GB of free space, try doing Microsoft Updates before trying the upgrade again.
