Update
Its not just the A button, I think what's going on is when you are on a screen that says 'press any button to continue' you can still move in the game would for one space before the game loads the next level. Therefore if A was a valid move you will be moved, this move will uncompleted the level after witch the next level will be loaded but because the previous level is now uncompleted it stops movement in the now loaded level. This is all speculation, I have no idea on how the game works internally, hope this helps in fixing it.