HP 830 G9 - external monitor problem USB-C

[Franciszek1]

Hello, I received a following problem from user:
"I have received a laptop (HP Elitebook 830 G9) last week and it seems like external monitor connection through UBS C is not working correctly.
I have an external monitor (LG 35WN75C) with built in USB C hub which allows to connect with a laptop and deliver display, power and peripherals through a single Thunderbolt 3 cable. This kind of set up works flawlessly with all my personal devices and my previous laptop (Dell Latitude 7400).

Initially when I tired to connect my new HP Elitebook 830 G9 with the same monitor through UBS-C I could see a black screen and my monitor's physical buttons were not responding (monitor was correctly detected by Windows). After an investigation I noticed that when I turn on Windows HDR option under Display Settings, the connection starts working (however the colors are washed out and it's not really possible to use the monitor with this option on). After that when I turn Windows HDR off the connection still works fine until the monitor is turned off or it goes into the sleep mode (essentially making this workaround not a viable option).

I have reinstalled display adapters, usb controllers and monitor drivers but the issue still persist.
I have also all mandatory and optional windows updates installed."
Is there a possibility that the 830 G9 do not support that kind of connection with external monitor or with that particular monitor?
Thank you

[Fwanck]

While not exactly the same problem, my Elitebook 860 G9 has similar problem. Monitors whille flicker/trun off/lost signalusing a USB-C dock.

I did not have this problem with my previous G6 laptop.

We are also seeing this happend to EliteBook 840 G9 laptops.

We are fully updated an no fix.

We have sent a unit in at HP for diag/replacement.