Cannot upgrade Windows 10 - Booting external

I'm booting off an external USB 3.0 dock - an Inateck FD2102, with a Western Digital blue SSD and a 1tb Seagate, although that is irrelevant.

I installed Windows using a USB device, normally, then moved the drive to the dock and reset through automatic repair to get it to work as a bootable drive. Unfortunately, my install media was Windows 1607 and I want to upgrade to Windows 1803.

I've tried the registry trick (Setting PortableOperatingSystem to 0) and used the Windows Setup tool (not in settings) to attempt the update, but it just bootlooped then reset me to Windows 1607.

Windows 10 Setup reports error 0x80073BC3 - 0x20009.

I would prefer to not go through the 2+hr process of cloning data, and going through the whole process again every time a new Windows version comes out, but I can't find much info online.

Before we try to install Windows 10, please ensure the machine has got the latest updates and we could unplug all the external devices temporatily.
If the issue persists, we could try to upgrade in clean boot environment to have a check. How to perform a clean boot in Windows
https://support.microsoft.com/en-us/kb/929135

If it is possible, please upload the log to OneDrive and paste the link here. We may get more information from the log to troubleshoot this issue.

If it still not work, just install win10 1803 by USB.