MacBook Pro 16" 2019 Mirroring issue with 4K display

[hajime]

Hi, I am using the Apple USB-C to Digital AV Adapter to connect my MBP 16" 2019 to an external 4K TV which has a default resolution of 3840x2160.

https://www.sony.ca/en/electronics/televisions/xbr-x900e-series/specifications

When the MBP is at default resolution, setting mirroring to external display caused the upper part portion of the MBP turned black (like the entire desktop is squeezed in the vertical direction). Is this normal?

If I use EasyRes to set the resolution to 3820x2160 60Hz, both the upper and lower parts of the MBP turned black and the desktop is squeezed even more. Anything wrong?

 

[hajime]

I spent over an hour with Apple Support. A support agent and her senior could not solve the problem. The agent even mentioned that the Apple USB-C to Digital AV Adapter only supports 3840x2160 at 30Hz even on their website it states 60Hz.

What I don't understand is that the senior guy mentioned that for mirroring, I should adjust the resolution on the MBP to match the resolutions of the external display. I asked him a few times to confirm and he said yes. In this case, I should adjust the resolution of the MBP to 3820x2160 as my TV resolution is that. However, as mentioned in #1, doing so caused both upper and lower parts of the MBP screen turned black.