The digital clock inset in the tach, the cluster LCD, and the factory head unit are all known to lose pixels with age. This is treated as an easy, expected fix rather than a dealbreaker: specialist rebuilders (Atlanta Speedometer around $350, Southern Electronics of Richmond) restore the displays, and some sellers replace the LCD screens outright before sale.
Instrument cluster and radio dead pixels / LCD failure
Mercedes-Benz CLK55 AMG (C208) · cosmetic