Macbook Pro gets slow frequently when connected to external monitor via HDMI cable

Hi I have a Macbook Pro (2019). Both my laptop and external monitor is getting slow frequently when i connect to a LG 4k external monitor. I am using typec to Hdmi adpater to connect to monitor.

My Laptop details:

Also when this happens videos are getting pixelated (can be seen in the below image).

All I can see is that my kernal_task is consuming too much cpu but not sure why this is happening.

I have took some screenshots of temperatures from tg_pro app when this issue occurred, and it seems fine.

Any Idea, How I can fix the issue?

This looks like you have a faulty cable and I would look into replacing that immediately. The faulty cable is also causing the performance issues as kernel_task with such a high CPU usage means it is thermal throttling hard.

I've always used the Choetech brand for my USB-C to HDMI but PrimeCables will do as well. Make sure you're getting something rated for 4K 60Hz and check the reviews on whatever you intend to buy. As an aside, I'd look into a USB-C to DP adapter instead as this can result in a better experience with certain monitors.