OK, I have just finished my tests and have several hours of video material which I have to edit before it's undestandable. It will be here earliest tomorrow morning, might even be tomorrow evening.
Anyway, here are the results of 16 hours continuous installing and sysprepping and failing and finally finding a working solution which I can now reproduce at will, every time.
1.) Build 9926 Pro edition (from Windows Insider) fails the sysprep every time on vm and two thirds of tries on real machine (my subjective, not automatically factual statistics). This seems to be (comical enough!) due Windows Insider app. Checking the error logs there's various errors every time, but always something common: "Package Microsoft.InsiderHub_184.108.40.2060_x64 was installed for a user, but not provisioned for all users". I tried removing the AppxPackage Microsoft.InsiderHub before sysprepping, did not work. Also trying to install offline, vm not connected to network when installing to avoid installing the Hub in the first place did not help, however logical solution that had been.
2.) Build 9926 Enterprise edition (from TechNet Evaluation Center), sysprep and customizations work every time like a charm as long as you remember to disconnect the computer or vm from the network before starting to install. As soon as you have arrived to desktop in Audit Mode you can reconnect the computer and download ADK and software to be installed. When connected to network while installing, all vm syspreps failed and over half on the real machines. As soon as I tried to install network disconnected, my success rate was 100%.
3.) You cannot create a catalog file (Part 5 Step 5.6 in this tutorial) using the install.wim file in Build 9926. Use Windows 8.1 Update, or Windows 10 Builds 9841, 9860 or 9879 install.wim. When you have saved your answer file, open it with Notepad and edit the highlighted part in below example answer file, everything between the double quotes. In this example it is wim:X:\Sources\install.wim#Windows 10 Enterprise, meaning that the Windows install media and its install.wim file used for Sysprepping (which as told above is not the same we use for catalog) are located on drive X:.
4.) The above answer file works if you want to save time and copy it, just editing the customized OEM information and path to Windows install media, I sysprepped my main image now with it. Although the whole process, from starting the install, to Audit Mode and customizations and finally capturing the image with Macrium took 1 hour 45 minutes, I am happy and satisfied; In my final tests I needed just 9 minutes to restore that image, getting a virgin clean installed Windows which is to begin with highly personalized and includes all my software.
<?xml version="1.0" encoding="utf-8"?>
<component name="Microsoft-Windows-Shell-Setup" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<SupportPhone>+1 (202) 456-1111</SupportPhone>
<cpi:offlineImage cpi:source="wim:X:\Sources\install.wim#Windows 10 Enterprise" xmlns:cpi="urn:schemas-microsoft-com:cpi" />
That's about it. A complete video tutorial follows as promised.
Just for bragging purposes, this is what I get on a real physical machine with totally wiped HDD exactly 13 minutes after I have booted it up with Macrium WinPE disk and restored the sysprepped image ( (9 minutes to "Enter you MS Account", creating the first user account and then 4 minutes "Windows is installing your apps" and such):Every customization I made in Audit Mode, every application is pre-installed:The best of it is of course that this is a hardware independent image and can be restored (installed) on every PC capable of running Windows 10.