A thought guys what if the checksum is only part of the requirement

During installation these files are being written to memory in the Nav Computer what if they have to be a very specific size in order to be placed in the correct position in the firmware and if the installer can't write the files to the correct area of memory it just bombs?

Or could it be that once the installer has written the files it then writes something else somewhere that tells the Nav comp bios what is where?

And it is at that stage that things don't add up so it bombs again?