when I incert a game, it tells me an error has occered

when I put a game card in the game will not show up on my screen... sometimes. If iI push the came card down until I hear a "click" sound it wont work. however if I slowly push down (and not all the way down) turn off the power and start it back up my game will show up and i can play it. This would be great if it didn't work half the time. Sometimes i start to play it and it tells me an error has occurred. other times it won't let me save, and sometimes it will work perfectly. This is all on a 3ds by the way.