Months after Screen replacement backlight is going out

Hello all,

I'm here at a business that repairs cell phone screens, we are one of the few that are certified to open a phone without voiding the warranty. We've been having issues with the backlight going out months after a simple screen replacement. Any ideas as to why that would happen?

Long screw issue?

Just fyi we always disconnect the battery when doing repairs, as we know that replacing a screen with it connected can cause the backlight to be damaged.

Any suggestions are welcome.

Thank You!