Why does my screen go dim randomly on Lollipop 5.1?

[AC Question]

I'm using Android Lollipop 5.1 my phone is a Bush Spira C1 5" 4G Lollipop 5.1, when I'm using my phone, I have the box "Adaptive Brightness" unchecked & the brightness level slider set to my preferred yet, the brightness will change by it self.

Is there a fix to this? I appreciate any suggestions that are given.

 

[Nikolas Crisci]

My brightness changes if my power scheme changes e.g.: if you are low on battery, is that the problem? If not how often does it happen?