multi boot - What could be causing Windows updates to fail?

I have a multi-boot system with Ubuntu 16.04 and two copies of Windows 10. The partition layout is as follows:

/dev/sda1, file system = ext4, size = 30.52 GiB, label = Ubuntu 16.04
/dev/sda2, file system = ntfs, size = 64.00 GiB, label = Windows 10 (1)
/dev/sda2, file system = ntfs, size = 64.00 GiB, label = Windows 10 (2)
/dev/sda4, file system = extended, size = rest of drive

Every time I attempt to install updates under Windows 10, it fails in the installation process displaying

"We couldn't complete the updates. Undoing changes. Don't turn off your computer".

I've ran the Windows 10 Troubleshooter, which fails with the error

"Windows 10 service registration is missing or corrupt".

I tried the fix on the Microsoft forums with no luck.

I brought up Windows 10 using a different drive but on the same machine and I was successfully able to download and install all updates. Using DiscWizard, I imaged that installation and restored it to "Windows 10 (1)" on the first drive and was unable to install updates, receiving the same error.

Could the existence of the Linux partition be confusing Windows? Or possibly Windows doesn't like being booted from Grub 2? I'm all out of ideas.