Windows 10 Version 1607 in-place upgrade freezes in the middle of the in-place upgrade while the Upgrade Operating System task is running. Usually a good indication that you are running into the problem is that Windows Setup freezes during driver inventory.
You can see this in the setupact.log under the C:\$WINDOWS.~BT\Sources\Panther\.
For example:
Date Time CONX
Windows::Compat::Appraiser::WicaDeviceInventory::GetInventory (324): Starting Device Inventory.
Date Time CONX
Windows::Compat::Appraiser::DriverInventory::GetInventory (204): Starting Driver Inventory.