This may be a glitch. but I have serveral ideas for the solution.
-soft reset (Lb Rb Start Select) at the same time
-restart your gaming device.
-take out your game, blow air into the cartridge and game, and then insert back in and try again.
Erase your data.
Keep in mind, try not to erase your data, and try different things. it might be a fault in the game it's self (game card). If the warrenty is still active and you already reset your data and it still glitches, contact your store that you bought it from. they may have a solution.