I have SV203 board for my robot arm project. When I power on (either battery or power supply through adapter) properly to the board, the servo motor did not return to its neutral position. Instead, the servo motor moves a bit when I touch the terminal to battery on and off. It is kind like it moves a bit incrementally every time we 'actuate' the board with power supply. But I thought the motor should be able to move smoothly to its neutral position continuously when it is powered on. I have checked all the wire connection. There should not be inconstant power supply problem because the same thing happened when we used power supply. Can anyone please advice. Thank you.