Thunderbolt dock WD22TB4 slow speed on Thunderbolt 4 port and USB-C 3.2 port

Hi guys, 

I have issues with my thunderbolt dock WD22TB4. I have two external SSD drives, both with type-c connections with the maximum speed of 10 Gbps. 

Case 1: Connect the dock to Dell laptop Latitude 5430. Then connect the external SSD drive to either thunderbolts 4 port or USB-C port, the speed to copy a 15 Gb file is only around 40 mb/s. But when direct connect the SSD drive to Dell laptop, the speed for copying the same file is around 800 mb/s, which is normal. This happens on both external SSD drive. 

Case 2: I also tried to connect the dock to the Ipad pro, and tested with this configuration, the speed when SSD drive is connected to the dock is also only 40 mb/s; but can get around 800 mb/s when direct connect external SSD drive to iPad pro.

The dock firmware is updated to the latest version, not sure what is the problem, is anyone can help to advise?