A Mario Kart 7 Cartridge will work sometimes.

Long story short, I said i would fix it for a friend, Once cleaned it would work flawlessly, but two days later i get "The game cartridge has been removed" and I clean it again, then it would work, He did say that it did get a little water damage on the pins, but with isopropyl alcohol it would work for a little bit.

I need answers please, Thank you.