HP ZBook 15V G5 Dual Display 4K dock

[saadzmirza]

Hi, I recently bought two 4K monitors from Innocn 28D1U on sale:

https://innocn.com/products/innocn-28-4k-uhd-computer-monitor-refurbished-28d1u?variant=443326653401...

This is my PC:

https://support.hp.com/us-en/document/c05994905#AbT4

I purchased the following three docks:

https://www.amazon.com/dp/B0B1PT5FVM?psc=1&ref=ppx_yo2ov_dt_b_product_details

HP Thunderbolt Dock G2 230w combo cable which is recommended by HP for this device

Belkin Thunderbolt 3 Dock Plus

My computer is an HP ZBook 15V G5. It supports Thunderbolt 3, DP 1.2, and USB 3.1 out of a single USB-C port. I want to be able to run both monitors at 4k at at least 30 Hz off of a dock off the single USB-C plug. According to this guide, CONFIGURING MULTIPLE DISPLAYS ON HP ZBOOK 15 G5 G6 AND G7, the notebook supports up to 5 displays in hybrid graphics mode. 

It indicates that the notebook supports DisplayPort 1.2 per the ports below on page 4:

Page 6 describes that the HP ZHAN 99, which I believe is equivalent to the ZBook 15v G5, has a single DisplayPort stream.

Page 8 of the PDF indicates that with a single DisplayPort 1.2 stream, which I understand that the ZBook 15v G5 and ZHAN 99 notebook have, I should be able to achieve dual 4k 30 Hz displays connected to the HP Thunderbolt G2 dock. 

However, when I plug in this configuration, with both 4k monitors connected to the Thunderbolt G2 dock, one monitor works at 4k (don't remember the refresh rate), while the other flashes at a lower resolution, periodically disconnecting. I was not able to correct the issue in Nvidia Control Panel either. I was able to make both displays work by connecting one via DisplayPort cable to the HP Thunderbolt G2 dock, and the second display to the laptop's onboard HDMI port. Both are running 4k 60 Hz, which I'm happy with. However, I wish that I could run both monitors at 4k at at least 30 Hz off of a dock off the single USB-C plug. 

I thought maybe the HP Thunderbolt Dock G2 was defective, so I purchased a Belkin Thunderbolt 3 Plus dock. However, I experienced similar behavior with the HP ZBook 15v G5 notebook, where I wasn't able to run both 4k monitors off the dock.  I experience a similar issue with the Baseus USB-C dock.

To do a sanity test, I checked the behavior of the Baseus USB-C dock and the Belkin Thunderbolt 3 Plus dock with a Microsoft Surface Laptop from around 2022. This worked flawlessly with both monitors at 4k on both the Baseus and the Belkin docks. I was not able to test with the HP Thunderbolt Dock G2 because I only have the combo cable with barrel charger for this dock. This tells me that the docking limitation is within my HP ZBook 15v G5 notebook, not my docking stations.