We found the solution. It was because we were missing motor.setExpiration(0.1)
Code:
public Robot() {
stickL = new Joystick(0);
stickR = new Joystick(1);
controller = new Joystick(2);
LF = new Talon(0);
RF = new Talon(3);
LR = new Talon(1);
RR = new Talon(4);
LF.setExpiration(0.1);
RF.setExpiration(0.1);
LR.setExpiration(0.1);
RR.setExpiration(0.1);