When trying to upgrade windows 10 I got the following above error.  I did these steps for the MBR partion (view link for GPT) type and the update then worked:

  1. Press the Windows key + R. In the Run window that comes up, type diskmgmt.msc and press Enter.
  2. Select the partition marked System Reserve. Press-and-hold or right-click on it.
  3. Select Change Drive Letter and Paths.
  4. Choose Add.
  5. Enter Y for the drive letter.
  6. Tap or click OK.
  7. From the Start menu, search for cmd. Right-click Command Prompt from the search results, and select Run as administrator.
  8. In the command prompt, type Y: and hit enter to switch to that drive. Then, navigate to the Fonts folder by typing cd Boot\Fonts.
  9. Type the following and press Enter:
    takeown /d y /r /f .
    Note: You must include the space and the period after the “f”, or the command will not work properly.
  10. Back up the permission to the drive by typing the following and press Enter:
    icacls Y:\* /save %systemdrive%\NTFSp.txt /c /t
    Note: Make sure that all files are showed as successful and none as failed.
  11. Type whoami and press Enter, and then record the user name. Type the following command and press Enter:
    icacls . /grant <username you got from whoami>:F /tNote: Do not put a space between the username and “:F”, or the command won’t work.
  12. Make sure you are still located in Fonts location (Y:\Boot\Fonts) as described in step 8. Then, Type del *.* to delete font files. The system may ask you if you are sure to continue, press Y and then enter to continue.

References:

https://support.microsoft.com/en-us/help/3086249/we-couldn-t-update-system-reserved-partition-error-installing-windows