avant@avant
It's probably not a fault, it's most likely that the xbox was sold with fewer games installed.
You can use FlashFXP to compare two xboxes, log into each xbox side by side and go into the game location directories and press CTRL+D to show differences between directories, that will highlight which roms are missing. Â Then press CTRL+A to select all the missing roms from the xbox that has more games, then CTRL+Q to add them to the queue, and finally CTRL+Z to start transferring the queue.