Apple Configurator 2 failed to install iOS

Dear all,

I need to install a specific iOS-Version, but not the current one. I know how to do it with the Configurator, but get always this error:

Personalization failed[com.apple.MobileDevice.MobileRestore-0xFBB(4028)

I found solution for "4027", but not for "4028".

• The ipsw is from ipsw.me
• I use the Apple Configurator 2
• Installing the newest iOS via the update button works fine (But not my intention)
• It is a update and not a downgrade
• Installing the ripsaw of the current version brings the same error

Is it a possibility that the iPhone is not a free Phone but a "Remote Management"?

Thanks for the help.