[Q] Phone Brightness Won't Go Above 50%

I recently got my LG G2 repaired after shattering the front glass by dropping it on the street. The repairer seems to have done a half baked job. After repair, the brightness of the screen is unable to go above 50%. Raising the brightness slider up to 50% raises the real brightness of the screen normally, but past 50% there is no perceptible effect. This is not just me not "seeing" the change when it might still be there. It used to be that the slider was calibrated in such a way that the last 50% had a way bigger effect than the first 50%, so at 50% it's more like the brightness output is 30% (which makes my current problem extra annoying). The brightness is supposed to really take off past 50% and now it refuses to.

Just curious if anyone with technical hardware know-how knows what kind of defect causes a problem like this and whether it's possible to solve it. Thanks.