One solution is to replace UIAutomationCore.dll with the one from WinPE 10 1803. While this workaround does get the ball moving, I cannot recommend making this change as there is no way to know what using an older version will break.
Mohammed Feroze Khan came up with the workaround on Twitter
And the rest is history.
System.DllNotFoundException
A closer look at Nathan's error shows that there was a DLL not found.
System.DllNotFoundException: Unable to load DLL ‘UIAutomationCore.dll’: The specified module could not be found. (Exception from HRESULT: 0x8007007E)
A quick read would suggest that this is a problem with UIAutomationCore.dll ... but this is not entirely accurate. UIAutomationCore.dll threw the exception because it could not find a required DLL
WinPE Process Monitor
I ran a side by side test of WinPE from the ADK and WinPE from a Windows 10 1809 Boot.wim and added NetFX, PowerShell, ProcMon64.exe, and a simple WPF test.
When executing my WPF test, I immediately notice that it is PowerShell that is crashing as it drops from a PowerShell Prompt to a Command Prompt.
Since I have an App Crash, I get a Windows Error Report which shows the same System.DllNotFoundException
WinPE exported from the Boot.wim does not crash. Process Monitor shows it using the DLL BCP47Langs.dll
But BCP47Langs.dll does not exist in the ADK WinPE.wim , which explains Dll Not Found crash. This is evident in the Process Monitor results.
System.DllNotFoundException = Missing BCP47*.dll
Adding BCP47Langs.dll and BCP47mrm.dll to ADK WinPE makes everything work as expected. This is the proper solution
Recommendations
Copy BCP47*.dll from Windows\System32 of a Windows 10 x64 1809 and add them to your WinPE Extra Files to be copied to <WinPE>:\Windows\System32 or add these files in Offline Servicing.
These files are already in the Boot.wim's WinPE, so that explains why it works. These files are NOT part of WinPE NetFX Package, or the Cumulative Update, so copying from a live OS is the only way to go for now.
Enjoy!
Technical Notes
BPC47*.dll Files
Files are located in the following locations on Windows 10 x64 1809
