How do I stop my MacBook Air from automatically adjusting its brightness?

I've gone and unchecked the box in the 'displays' tab in system preferences that says 'automatically adjust brightness'. However, my Mac continues to adjust its brightness randomly. I usually work in a well-lit room, which in this case i'm not sure if that may be causing this problem to occur. Also, my laptop has lastedme for some time and possibly may just be getting old. Nevertheless, this brightness situation has been occurring for a while now and I find myself furiously tapping away at the 'increase brightness' key whenever it decides to dim. I recently updated my computer to the 'High Sierra' operating system and nothing has improved.

(These are just some specs of my MacBook Air)