Problem with connecting Zenbook 14X OLED to LG Ultrafine 4K

[Torstein]

System: Zenbook 14X OLED
Battery or AC: AC
Model: UX5401 11th Gen Intel
Frequency of occurrence: Always
Detailed description：
I have an Asus Zenbook 14X, which slows down dramatically whenever I connect an LG Ultrafine 4K (24in) display via Thunderbolt 3. The image displays just fine on the screen, and everything appears to work fine, but as soon as I try to do something inside of Windows, everything is frustratingly slow.
I run Windows 11, and have installed all available updates. I've updated the Bios to v303. The computer behaves normally whenever the display is not connected, but as soon as I plug in the display cable, everything slows down by a lot. For instance right clicking the desktop takes over a second before the menu appears, and opening explorer can take 5 seconds instead of the usual 1. The image updates correctly, and the mouse cursor doesn't lag behind, but the CPU seems to be struggling. It sort of feels how you would expect Windows to behave immediately after plugging in something new, while waiting for the system to settle, without it ever settling.
I've tried mirroring the displays, and disabling the local display, without any apparent effect. I use the same display with a Macbook Pro, without any problems. Looking at the Performance tab inside Task Manager shows no particular issue with neither CPU, Memory nor GPU. But the GPU does idle around 10% instead of the normal 3% when it's connected. But it doesn't seem to peak above 25%.

[Jiaszzz_ASUS]

Hello Torstein and thank you for reaching out.
Could you please provide the full model name of your laptop? (for example, UX5401ZA or UX5401EA).
Does the situation you describe happen in duplicate mode, extend mode, only use the LG monitor as the main display, or all of the above?
Is there any specific program running when the situation occurs? For example, running Chrome, playing YouTube videos, or playing games?
Please conduct a cross-test using a different input signal connection (VGA, DVI, HDMI, DisplayPort) or another monitor if possible.
Thank you.

[Torstein]

Hi, thanks for the quick response.
The full model name is UX5401E.
The situation occurs in all modes, even when I in display settings only choose to display the on the internal display, with the external display just being plugged in - showing no image.
There are no specific programs running. Everything is closed, and the slowdown seems to be system-wide. Opening any program is slow, from calculator or explorer to chrome, the right click menu takes a while to display, and rendering web pages takes a loong time.
I did a few comparisons, and opening a fully closed chrome browser and loading a default page (vg.no) until completion takes around 30-35 seconds with mirroring or extended (browser on internal display), around 20 seconds when displaying only on the internal or the external display (no apparent difference), but just 2-4 seconds without the display plugged in.
If I connect the laptop to my LG 38WN95C (3840x1600) with the same Thunderbolt 3 cable, everything works fine. So it doesn't really feel like it's the resolution being the problem (even though the Ultrafine has a 35% more pixels with its 3840x2160 resolution). It feels more like some driver issue.
The LG Ultrafine only has USB-C/Thunderbolt 3 input, so I'm unable to test with more signals.

[Jiaszzz_ASUS]

Hello, Torstein.
After checking, it seems that the LG 38WN95C has provided a new driver update file for Windows on 2023/1/2. Please check whether there is an updateable driver and then confirm after updating to see if the operation is still sluggish.
At the same time, it is also suggested that you contact LG customer service and seek assistance related to the driver if needed.
Thank you.

[Torstein]

Unfortunately, the 38WN95C is the display that works fine. So I don't think updating the drivers for that display will change how the UltraFine 4K behaves. And the UltraFine 4K doesn't have any driver updates for windows.