Computer worked fine for a couple of weeks.

Hardware specs:

• CPU: AMD Ryzen 9 3900X 12core


• Memory: 64GB Corsair


• GPU: Sapphire Radeon RX 5500 XT NITRO+ 8GB


• Motherboard: ASUS ROG Strix X570-F GAMING


• Wireless keyboard and mouse


• monitor: 4K 60Hz

Problem:
Computer freezes. It freeze most frequently when watching video in browser, after a while sound stops, a few seconds later computer is in this state:

• I can move the mouse-cursor, but clicking does nothing.


• Ctrl + Alt + F1 does nothing


• Short pressing the power button does nothing


• Picture is frozen except for the mouse cursor moving


• Same problem when connecting another keyboard and mouse


• SysRq REISUB works

Debugging different resolutions:

• No Problems: Resolution 1920 x 1080, Refresh rate: 60Hz Scale: 100%


• Fails: Resolution 3840 x 2160, Refresh rate: 60Hz Scale: 100%


• Fails: Resolution 3840 x 2160, Refresh rate: 60Hz Scale: 125%


• Fails: Resolution 3840 x 2160, Refresh rate: 60Hz Scale: 150%


• Fails: Resolution 3200 x 1800, Refresh rate: 60Hz Scale: 100%


• Fails: Resolution 2560 x 1440, Refresh rate: 60Hz Scale: 100%

Debugging:

• htop: CPU is below 10%


• watch sensors: CPU heat is around 50C, CPU power consumption is about 5-10W


• tail -f /var/log/{messages,kernel,dmesg,syslog}: didn't give any messages that looked interesting, last error before crashing was some DNS stuff.

Does anyone have a suggestion how to debug this problem?