S3225QC, 120Hz flicker

I got my new Dell S3225QC OLED monitor. Everything is fine and working great, but when I switch to 120 Hz (or any other frequency different from 60 Hz), the monitor starts to flicker and show artifacts. It's connected via HDMI. I bought a new, good HDMI cable (UGREEN Ultra High Speed HDMI 2.1), but nothing changed.

The latest Nvidia drivers.

The Dell monitor driver is installed.

I have updated the monitor firmware.

Next, I want to test 120 Hz with my laptop over USB-C to see if the problem is with my PC or with monitor.

Does anyone have any ideas to try?

My specs:
Win 11
Ryzen 7 9700X
32GB DDR5 6000
ASRock B650M Pro RS
MSI 5070ti