Light band on LCD display: LCD or Logic?

I whipped out my good old PSP 2000, date code 7C, serial ending in 276.

I noticed however, after some time of use, that the display has a vertical band, 5 pixel wide, that looks... lighter than the rest, like the colors were less strong.

When I put in pause a game is really evident, otherwise is faintly there, as the display gets grey, and the band gets a lighter shade of grey.

Is that a Logic, or a display issue?

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