Brightness at 0% after screen replacement

Hi, I hope you can help me with this.

My Moto G 2014 fell off and I got a nice Moto G with a broken display. I got a new display (all front module) and installed it. All is working fine but brightness, when I try to set it above 0%, it doesn’t change very much (just a subtle change from 0-10%, but not very noticeable).

It doesn’t matter how high I set the brightness, it just doesn’t change. However, when I try to set it below 0% using some apps, the display can go down until it is completly dark.

I was wondering if it could be a problem of the new display or a problem with the motherboard. I’d like to add that after the old display broke, the mobile phone got very hot for a while and then cooled down. Could it be that the backlight IC has been damaged, or it’s more likely a display problem?

Thanks in advance.