When you use the Reset this PC feature on Surface Studio, the action may take an extended time to complete or seem to stop at 8-percent completion.
This issue occurs due to the Hybrid Drive configuration and because there are additional languages included with the image.
When the issue occurs, don't turn off or restart the device during the process. We recommend that you let the process complete fully, which can take up to 10 hours, depending on whether you select Just remove my files or Remove my files and clean the drive.
The issue can also occur if you use Surface Data Eraser (SDE) tool to securely erase the drive.