bluetooth hand-free UNKNOWN caller ID names

My iPhone 7 iOS 10 pairs with my Citroen C5 internal hands-free (RNEG Myway FW version 50.03)

When I get a call, if the caller ID has more than 10 chars in the contact name, it will appear as UNKNOWN.

The same happens if I place the call trough the iPhone.

It works fine If the call is placed trough the car dialing interface.

As an example, there is no problem when using my iPhone 5S with iOS 9 ...