If that is the case, this is the reason why we recommended you to post this issue in the Feedback Hub. By posting this issue there, our Support Engineers can see your issue and examine it to determine if there is an error in the update. If you've already posted the issue in the Feedback Hub, it is best to share your submission here so that other community member can see it.
Please take note that the disk space is not the cause of the issue. If the issue is with the disk space, Windows Update will produce a different error code and error message. The partitions in your hard disk is also not the problem because you're able to install Windows 10 in a new partition. The issue that you're encountering with the update is already in the code of Windows 10 and the only one that can decipher the codes are the developers. This is why it is best to replace the whole system files of Windows 10 to resolve the issue.
Best regards.