Nice game, its kinda like Tetris. I'm not sure if this is a bug or not but after a while when the speed picks up sometimes 2 players spawn instead of only 1, though you can control both at the same time.
As to your issue, spawning 2 guys was designed as a mechanic. the chance of spawning 2 guys increases with your score. the mechanic needs work though because it makes it way too difficult when they spawn on opposite sides of the field.
