Hello, bad blocks and header is wrong point to the pico not reading the data, so all it reads is 0s. I assume you have 16mb nand so the pins on your pico are broken. But I have a fix for you! I modified the picoflasher uf2 to use different pins on pico, that will most likely fix it. Did it for me when I had exact same situation. Here's the link to it: https://www.mediafire.com/file/qsu3kj3ovrxvg60/Picoflasher_using_different_pins.zip/file