I don't use Windows 10, but I installed to a VirtualBox VM fresh Windows 10 and couldn't reproduce this.
Can someone post the error details from the event viewer? This should tell us the DLL it crashed on. Maybe we'll find a common non-Avast 3rd party DLL that is the cause. I have read many stories of Intel AMT software causing this problem if it is not up-to-date after other applications are updated (ie, common shared DLL changes).
It's my understanding that taskhostw.exe is the "Host Process for Windows Tasks", or a fancy way for Windows to run a DLL like an executable. The process crashing on shutdown is not a big showstopper, just an annoyance since a shutdown is just trying to end the processes under it's control anyway.

Does making the machine sleep instead of shutdown work around the problem temporarily?