(Question) Trying to modify region binary to replace stuff in minecraft world using blockdata

[julianprincipe]

I'm trying to write a simple script that replace NBT tags in a world, i'm testing it with a brand new world with a simple "give" command in a command block:

give @a golden_axe

My idea is to use get_blockdata() to unpack the binary, binary = binary.replace(b'minecraft:golden_axe', b'minecraft:golden_sword') to replace the item and write_blockdata() to write it to the file

This is the code i have:

for region in world.iter_regions():
            process_region_file(region, start, stop)
            for i in region.get_metadata():
                x = i.x
                z = i.z
                binary = region.get_blockdata(x,z)
                binary = binary.replace(b'minecraft:golden_axe', b'minecraft:golden_sword')
                nbt = region.write_blockdata(x, z, binary, compression=2)
                print(region.get_blockdata(x,z))

The code works with really specific stuff, i've managed to change random text in a command block but whenever i try to change items in a "give" command or something like that the command block just disappears.

I've manually checked the replacement by printing the binary and it works: Command\x00\x1cgive @p minecraft:golden_axe gets replaced to: Command\x00\x1cgive @p minecraft:golden_sword in the binary, but when i open the world the command block isn't there and if i check the binary after opening the world it just disappears from the binary aswell

Any ideas why it happens? Would you approach this idea differently? I'm really confused