Some LED failures will show with dark spots on the bottom edge. But maybe difficult as backlight will shutoff quickly with increased brightness making it harder to see. LED tester can reveal failed LEDs after LED bar is removed.

Note each LED has a fragile yellow dome that converts blue light to white. These are easy to knock off. Take caution when removing the LED bar and white reflector bar.

The plastic reflector bar just above LEDs are very brittle. Peeling back the black tape. Sometimes an additional ultra sticky semi-transparent layer is below break all the T shaped bars on removal. Use Xacto knight to carefully cut the tape around the tabs to avoid breaking. Use hot glue help secure broken bars during reassembly.

Working the reflector bar is a little tricky, Remove the 2 screws on both ends. Push and unclip all the snaps and gently slide all T bars evenly to the opening to remove. 2 ends with connector is a little tricky getting out and back in.

Gently pull out the connector and use a fine flat blade and magnifying eye wear to release the LED connector.