Why is my bottom screen starting out bright and then fading?

Hi!

I recently opened up my old device and replaced some worn out button pads. Unfortunately, it looks like I introduced a new problem in turn, because the bottom screen becomes really faded and fairly unusable.

I’ve included a video showing what happens. When I open the device and turn it on, it starts out with typical brightness and clarity. Within seconds, the screen dims to an unusable level.

I’ve tried adjusting the potentiometer, but I could not get it to work. Your help and insight would be really appreciated to fix this.

Do I need to replace my screen? Did I break the potentiometer?