Hello and thank you for posting!
The behavior you describe is expected. To expand further, the maximum supported display refresh rate via the TBT3-UDZ docking station is 60Hz (and we do our best to call this out in our product listings) and HDR is not supported.
If you require a product that supports 120Hz refresh rates and HDR support, then I am afraid I would recommend making use of our 30-day no-hassle return policy to return the docking station to Amazon for a refund.
Apologies that we could not be of more help in this specific case, and thank you in advance for your understanding!
Bob
Plugable Technologies