Earlier quoted context omitted.
I've a similar setup and no problems. Perhaps try updating the firmware, and reseating the connections. If there are still problems perhaps some parts need to be replaced.
I just checked and I do have the latest firmware for both the laptop and the dock. The issue still persists. What is your motherboard version? Mine is A03. I had the initial one replaced. (I also replaced TB15 that was a total failure)
I have the TB16 also.