How do I stop a File Explorer window from opening after the source has been sysprepped.

Question

I have a Windows 10 machine configured the way I need. all windows are closed only thing available are the shortcuts on the desktop.

I copy a unattend.xlm file to c:\windows\panther

I open a command prompt change to c:\windows\system32\sysprep and execute sysprep /generalize /oobe /shutdown.

Process is successful.

When I power this machine back on it goes thru the boot process as expected and after all reboots are completed the desktop appears but a File Explorer window opens as well.

I cannot find why this file explorer window now opens every time the machine is rebooted.

I checked things like startup and runonce registry keys.

Any help is appreciated