Answer:
diffuser
Step-by-step explanation:
Based on the scenario being described, the most likely cause of the problem is a bad diffuser. This is a component found in nearly every type of LCD backlit displays and are used to produce an even array of lighting across the entire display. If this component fails then it will cause bright spots and dim spots throughout the display, similar to what the client is reporting in this scenario since the light is not being evenly distributed.