Created attachment 180800 [details]
kscreen-console

Hello everyone. I stumbled over this bug weeks ago, ignored it then came back today to it to nail down when it happens. It might seem niche at first, but for gaming pc setups I believe it is actually a widespread scenario. The question is, can anyone reproduce this or is it just me?

Steps to reproduce
- Nvidia GPU. Driver version currently at 570.144
- Two (or maybe more) screens connected to the card. I have used DisplayPort cables. Tried different cable with no effect.
- Wayland only. Couldn't reproduce in X11.
- KDE Plasma 6.3.4 or git-master on arch, can repro on both.
- Set the screens to different refresh rates. Some people may wonder, why would anyone do that? Usually gamers might want to do that, to have one screen for games and other one with lower rate to save energy. Yes that seems weird if your card easily consumes 200 W when playing, but you gotta offset that somehow, right?
- Pull up the "Brightness and Color" icon from the system tray. Change around the sliders a couple of times. Happened at second or third time for me, sometimes more often. You should see the freeze instantly because it appears on the same screen where the slider is.

BUG VIDEO DEMONSTRATION
Please see the video here: https://youtu.be/HxjlQFm3jhI
The crash happens around 01:28. To my amazement you can actually see the right screen freezing and left screen working OK. The primary screen stops updating content entirely after that.

OBSERVED RESULT
The screen selected as "Primary" screen in Display Configuarion stops updating its content. As I can't kill my desktop session with ctrl+alt+backspace and I usually can't log out using GUI at this point, I have to reboot system to recover. 

EXPECTED RESULT
No screen is freezing.

System Information: 
Operating System: Arch Linux 
KDE Plasma Version: 6.3.80
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
Kernel Version: 6.14.2-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 x AMD Ryzen 7 5700X3D 8-Core Processor
Memory: 32 GiB of RAM (31.3 GiB usable)
Graphics Processor: NVIDIA GeForce RTX 2070 SUPER
Manufacturer: Micro-Star International Co., Ltd.
Product Name: MS-7B85
System Version: 1.0
nvidia-open-dkms 570.144-1

ADDITIONAL INFORMATION

Noteworty:
- Bug was introduced to my system in the last couple of weeks. It definitely worked a couple months back, as I used that slider daily. Arch shipped upgrades to both nvidia drivers and KDE Plasma in the meantime.
- Bug is not reproducible on my amdgpu laptop with external screen
- Bug is not reproducible in X11

See output of kscreen-console and kscreen-doctor -o in attached files

Since the workaround here is changing the refresh rate each time you want to change the brightness, I'm gonna give it severity "major" (with no known workaround, or the workaround is painful and difficult)