This solution below might possibly help solved the problem for it shows the display data signal line paths from the processor chip through to the LCD pin connector for an ease of troubleshooting.
Nokia 5220 Display problem solution - Display connection tracks
Each of the display data signals which feed from the application processor chip is filtered by a 330 ohms resistors before it reach up through to the LCD screen display module. You may start to check, trace from this components and way up to LCD pin connector.
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