This is a splitting & continuation from another thread.
With my 16" MBP with Catalina, connecting a display to the dock or waking the display up after it’s gone to sleep causes mouse motion to repeatedly freeze up for a fraction of a second every ~2.4 seconds. The effect tends to stop after a while, thankfully. However it doesn’t matter if the mouse/trackpad is connected through the dock, connected directly to the laptop, or if it’s the built-in trackpad - they all have the same behavior. Additionally the issue is not the display freezing up since I played a view behind the cursor during the problem, and while the cursor would freeze up the video continued to play.
At the request of @Joshua_H I ran tests with different configurations. With only the display attached to the dock, and the dock attached to the laptop with nothing else attached, the problem still occurred.
- HP2159m with both an HDMI-DVI and HDMI-HDMI cable - still a problem, regardless which HDMI port was used on the dock.
- NEC MultiSync LCD1960NXi with the HDMI-DVI cable - still a problem.
- LG 29UM55-P with HDMI-HDMI cable - still a problem.
I’m currently waiting for a DisplayPort cable to be delivered so I can also test that interface on the dock.