Upgrade from 1703 to 1709 fails on a number of workstations. All Pro

I have 3 workstations that continually refuse to succeed in upgrading from 1703 to 1709. All of the other workstations (over 50 of them) have upgraded successfully. They are similar enough that it's doubtful there is something wrong in the approach being used (just let Windows Update do it usually).

I've tried the Update Troubleshooter. I've turned off AV programs running (Windows Defender and Malwarebytes) to no avail.

Is there good advice re: how to get this upgrade to happen? I can't find it.

The affected computers:

Lenovo M900 64bit / Windows 10 Pro 64-bit (this is a rather new machine) .. reports Up-to-date
Lenovo 7522CTO ThinkCentre A58 64 bit / Windows 10 Pro 32-bit .. last Error 0x800704c7
Dell Optiplex 780 64-bit / Windows 10 Pro 32-bit

The only commonality that I can find is that each of these computers is my own workstation.....

In some cases, I got error messages that said there were various things installed on the computer that *are not* installed (e.g. Avira). Now, on the Lenovo M900, that message no longer appears but the install still fails.

I would wait about three weeks, then doelwnload 1803 iso, mount as drive and run setup.exe to manually upgrade.

If you look at your Update History, is there a history of 1703 update failures, or not?

Basics for upgrade problems:
- uninstall/disable/remove security software (noting your reports- if you've ever had those installed, might need to try a manual removal tool- or even check through the registry if all else fails.
- disconnect any unnecessary peripherals esp. wireless
- make sure there's 20Gb or more spare space on C:

Check your disk e.g. Hard disk sentinel (trial) or other programs; from an admin command prompt run
chkdsk c: /scan and check all is well- if not, run chkdsk c: /F
If ok from an admin command prompt run
SFC /SCANNOW

Try
Reset Windows Update in Windows 10 Windows 10 Tutorials

If ok, try upgrading manually using a downloaded iso, but without accepting updates during that procedure.

Then you can analyse the Windows update logs.
One poster here uses the log collection tool from the BSOD reporting section here.