12864 LCD – Missing Lines/Pixels
How to Fix
If your 12864 LCD has missing rows/lines of pixels it is because the screws are overtightened. Back off the screws and make sure the LCD PCB is not bending and the LCD will display normally again.
If backing them off does not fix it then remove the LCD from the housing completely and then put the screws in again, STOP screwing them in once the screw head makes contact with the LCD PCB.