Windows 10 Update Error 0x80070001

I had two Windows 10 machines which had stopped pulling upgrades from Microsoft for quite long (1703, anyone?) and I could not get it back working.
Windows Update just showed me the error 0x80070001 and did refuse to do anything.

Tried:
- Clearing Windows Update Cache
- WSUS Offline Patching (installed the updates, but the normal Windows Update did not start working after that...)
- Windows Update Repair Tool from Microsoft

Nothing did really work, until I stumbled upon a post by OksiQuatzel:
Culprit was the installed ImDisk, a virtual Floppy Drive. With this installed and an A Drive mounted - this error arose.
As soon as I unmounted the drive and removed the driver - everything started working again.
Kind of nuts that something like this could occur.

Actually I tried it with ImDisk, Virtual Floppy Drive 2.1 and other Virtual Floppy Drives and RAMdisk drives - there is a high chance that - if you use such a program, the Windows 10 Update does cease function...

Source in german