Sorry, but Super Nintendo's don't suffer from common ailments with their cartridge slots.

The chances of something peculiar being up with the cartridge slot of two different Super Nintendo systems that allows other games to play, but causes Super Metroid to display the same odd error, is slim at best.

Has to be a defect with the cartridge. I guarantee it will turn out that way if he investigates this further, or I give you permission to request me to be banned from this board if I end up wrong.