As I said, I've tried everything found on support forums, also with another computer - less powerful with USB 2 ports (nothing else connected, everything up to date).
No improvement. I value my time and if I pay 730€ for a product, I expect that it works as described in manual or your website.
There is no mention about these problems.
Anyway, yesterday I returned it to the store, they will send it for checking. If it does not improve, I will be obliged to sell it.
In that case I can't recommend your products to my students neither. Pity.