Apple Configurator can't update iPhones > 5S

Hello,

I got a mysterious problem with my apple configurator:

All iPhones which are newer than the 5S can't be updated.

Here are the facts:

- Apple Conifgurator 2 (latest version) on Mac OS 10.11.6

- Works fine with iPhone 4/5/5S

- Does not work with 6/6S/SE

- Everytime the update fails I connect the iPhone to my iTunes (on my Windows PC) and restore it.
(ITunes on my Mac wasn't able to restore the iPhone.) From that day on Apple Configurator works fine.

Here is what I tried to conquer this problem:

- Upgraded to Apple Configurator to version 2.

- Made a complete fresh install of Mac OS X.

- Tried a new cable.

All of this things don't change anything.

Does anybody know this problem?

Thanks for any help.

Best regards,

PM_SSW