Some monitors have firmware bugs and don't react well to DDC commands.
You may first try to increase the DDC Sleep Factor to Medium or Long:
If the problem persists even with the DDC Sleep Factor set to Long, you will need to disable DDC completely.
To do that, disable Hardware (DDC) controls from the gear ⚙️ icon menu:
Lunar will fallback to adjusting brightness and contrast in software using Gamma values.
Notes about Gamma:
- Conflicts with other apps that use Gamma like f.lux so you have to quit them
- Night Shift is a good alternative as it doesn't use Gamma
- Can only lower the brightness, not increase it
- That's why you have to manually set the monitor brightness and contrast to maximum using its physical buttons
- Can't change the volume or input of the monitor
- Those features require DDC