Wheels rotates in different direction (Bluetooth Self Balancing Robot)

No I mean like this:

  1. both wheels have the same direction when forward and backward. It's balanced enough.
    2., BUT => he turn around (the BODY of the robot turns around and going forward and backward. I don't like to see him like that.

When I make an ONLY self-balancing robot, he didn't like that. When I use bluetooth with that codes, he goes crazy.