This shouldn't be possible, right?
Petroleum filled the spots/tank of rocket that is not there and then started flowing to the rocket on the right. (also all solid oxidizer tanks dropped their content because oxylite was unselected on load)
Or maybe every fuel tank spawns empty on load?
Take a look at the rockets on top. Unpause. Inputs of liquid fuel tanks are still visible and filling with fuel while the rocket is not there. Every fuel tank is empty and solid oxidizer tanks drop their oxylite