Support Screen dims while charging, but not in use

I use my phone (plugged into a car charger) to listen to podcasts in the car. I set the option for the screen to stay awake while charging, but after a period of inactivity (not sure how long), the screen will dim to the point that I can't see the interface.

Is there another setting I need to adjust to make it so the screen doesn't dim while it's charging?

 

As I mentioned, I have enabled the stay awake feature (which is under developer options). The screen stays awake, but dims after a period of inactivity.

 

Daydream was on, but turning it off didn't help.

I do not use auto brightness.