Very noisy mixer

The first mixer was received a lot of noise at low flow hot water. Mechanical sound like squeaking or squealing linked to the passage of water, noise that propagates in pipes and means throughout the house.
I started by contacting the customer service Grohe: no response for 15 days!
I finally requested the replacement of Amazon who answered in a heartbeat! Congratulations.
The new mixer is also making noise but less.
By buying this brand I expected quality equipment and efficient customer support. It is missed.

Thank you to the Amazon customers who kindly answer my question.

[Update] Grohe finally replied. According to them, the noise may be due to a manufacturing problem or a dynamic pressure difference on my installation. As the second mixer makes less noise than the first I deduce that this is more of a manufacturing problem. On the advice of an Amazon customer, I also tried to close a bit the inlet valve to the meter, but it does not change.

I will ask a new exchange to Amazon and if it continues I change brand.