I have now two further kernel issues with regards to graphics, but in both cases, the issue is limited to some devices that are attached by graphical interfaces (likely both hdmi). This means, one device attached and the issue appears, once the device is exchanged by another one, everything works fine. [1] [2]
Both have amd, but this can be a coincident if the bug is not amd- but hdmi-specific (or specific to something else with potential for graphics impact). Is it possible that you try to work with kernel 6.3.8 with other monitors, beamers or whatever?
Also, can you identify the supported HDMI version of your machine and the monitor (and if you can test with other monitors, also of these monitors).
Of course feel free to test any monitor/beamer you have, not limited to HDMI. We want to know what works and what not.