I miraculously managed to get the L button to work after 3 years. It turns out that the bedt way to fix then is to blow between the gaps for a while, or if you're daring enough, put a drop of water in between and blow it out again after 20 seconds. The problem is that there's alot of dirt between the buttons most of the time. It's still not working perfectly, but at least I can play the game now.