I have been in a world of pain this week because of this update.I was puzzled by why a Windows re-install would work for a while and then stop - it took me a while to realise it was this update, as I had originally assumed that the MediaCreationTool was creating a version of Windows prior to 1803. In fact the current MediaCreationTool creates 1803 (17134.1) and then at some point the 1803 update kicks in ( I have been installing from a USB created by the MediaCreationTool tool:Download Windows 10 )

One error I got was this one:
'The partitions on the disk selected for Installation are not in the recommended order. For additional information about installing to GPT disk go to the Microsoft website and search for GPT'
However, it (the media created from the MediaCreationTool) still installs on the main OS partition, copying the current Windows to Windows.old, Windows.old.000, Windows.old.001 etc.

Another problem I had was that one of the installs wouldn't update anything (Windows Update was broken).

I have disabled the problem 1803 update using wushowhide.diagcab. I'll have to keep an eye on whether that works or not (i.e. prevents the update).