Getting error 0x800703ee when trying to upgrade Windows 10

When I try to upgrade Windows 10 from version 1803 (build 17134.829) to version 1903 (the "Windows 10 May 2019 Update"), it almost finishes installing the update but then fails with error 0x800703ee: "We can't tell if your PC has enough space to continue installing Windows 10". I have 159 gigs free on my C drive so I don't know why it's complaining. I suspect that something in my computer is broken ever since I screwed up when migrated files from my HDD to my SSD.  (I had to repair Windows through USB recovery; it was not fun.)

Here is what my partitions look like currently:

C: is my primary SSD and D: is my hard drive.

Windows update log: https://pastebin.com/Z1RETXp4 (doesn't seem to have any useful details).

What I've tried:

• rebooting, then trying the upgrade again
• rebooting with non-Windows startup services disabled
• Installing update from ISO with the Internet turned off
• running DISM.exe /Online /Cleanup-image /Restorehealth
• ran sfc /scannow. Didn't find any problems.
• ran Windows Update troubleshooter and tried upgrading again

Other people have run into the same error: https://www.reddit.com/r/Windows10/comments/85hfrw/getting_error_code_0x800703ee_when_trying_to/

It's been happening to a few unlucky people ever since 2015 (maybe earlier): https://answers.microsoft.com/en-us/windows/forum/windows_10-windows_install/windows-10-install-cannot-determine-space/ca24594d-51a0-48b6-a504-ecf3b2dd20fc

Edit: I gave up and reinstalled windows from a usb

The reason you can't update is because you have no "system reserved" partition, or none with that explicit label.

You will need to create a system reserved partition, as specified in the following Microsoft Answers forum: https://answers.microsoft.com/en-us/windows/forum/windows_10-windows_install/no-windows-10-system-reserved-partition-cant/8ee6cd40-8e5a-4ec6-9cc3-80a305a97eec

You would also be able to re-partition by booting a live Ubuntu USB and use GParted. GParted allows you to take a partition off the end of another partition which may work for you.

Partitioning drives is very very dangerous and any mistake will cause data loss, however this is not always the case. Take a full backup of all relevant data before taking any action.

Honestly I wouldn't do this unless you absolutely need to update and can't continue to use your PC without updating.