MacBook Pro Late2013 - USB/WLAN-Problems

... I get sporadical problems with my usb3.0-device that seems to be related to wlan.

The usb 3.0 device is a Freecom Quattro 3TB harddisc.

From time to time it gets disconnected from the system - partly instantly.

In these cases, the wlan sometimes disconnects as well.

By first assumption: 5 GB/s-USB3.0 interferes with 5 GHz-WLAN.

And actually: I isolated the usb3.0-cable with aluminium, so the error happens less often (but still happens).

Before I buy an expensive shielded cable (which might not work as well):

• Is this a known problem? (connected with new wlan-AC-standard)
• Can it be avoided by "doing" something on my mac (e.g. somehow reducing the power of the internal wlan adapter)?

... the problem is reproducable with a second freecom harddisc drive.

... the harddiscs work (via usb2.0) on my old MacBook Pro

... the harddiscs work with firewire800 on my new MacBook Pro