Taking this to an extreme, if you can’t gain access via software (unlikely if it hasn’t been updated in 5 years), you could disassemble it, locate the SPI interface for the NAND (assuming it uses SPI), and use something like an arduino with a loaded SPI reader sketch to read it. You can then pick it apart to find vulnerabilities, or just replace it.
Taking this to an extreme, if you can’t gain access via software (unlikely if it hasn’t been updated in 5 years), you could disassemble it, locate the SPI interface for the NAND (assuming it uses SPI), and use something like an arduino with a loaded SPI reader sketch to read it. You can then pick it apart to find vulnerabilities, or just replace it.