One of the cables had a crack in the Plastikumantelung. And lo and behold - no metallic shield in the form of wire / aluminum ect.
According to the standard S / FTP: Metallic shielding with additional metallic overall screen around the conductor bundle (screened foiled twisted pair).
The total screen can be configured as a sheet or as a mesh, or of both together (see twisted pair-Wikipedia).
On the cable is Cat.6 WTP 4x2AWG Strandded x4 cable pairs. Here the cable described in the product description have not been delivered ("loose goods"),
but rather simple unshielded UTP cable.
I have the cable still used because they work obviously. Who but an appropriate shield needed
should resort to another and probably more expensive, really shielded CAT6 cables.