Can a damaged NAND IC be repaired in an iPhone 11?

if a person with enough SMD soldering skills and access to the chip replacement then sure

if apple will repair it for you, then probably not, and if they did it would likely cost twice of what an iphone 11 is worth today in man hour salary.

Apple Support does not diagnose and repair to the component level at the Apple Store level (Genius Bar) or Apple Service Centers. Apple Support diagnoses and repairs or replaces to the board level. You could approach an Apple Authorized Service Provider about such a repair. At their discretion they may do a repair of that nature.

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