You're saying the servo is rotating at the same speed and in the same direction for all 3 signals: 0, 180, 360? I care more about direction then speed: for my servos speed varies very little in a very narrow band around the midpoint: the motor is stopped at 180, moves slowly a 183, faster at 185, full speed at 190 (just an example, I'm using milliseconds, not degrees to set up my servos)
If 0 and 360 make the motor turn in the same direction and you have checked with an other servo and with the other servo it works as expected (makes the servo turn all the way to one side and then all the way to the other side) then it must be related to your soldering.