I can not solve the problem. Servo in the biceps of his right hand always gets out with increasing degrees. It turns unclamping hands. All servos rotate counterclockwise. It did not get to set up your biceps. I understand only soldering motor polarity servo? For biceps should shrink with increasing degrees and be decompressed at 0 degrees? sorry for the English.
Yes the hk15338 are reverse polarity compared to the hs-805.
You can modify the hardware to reverse the wire on the motor, or you can use a software solution by using servo.setInverted(True) or with servo.map(0,180,180,0). Both the software solution will make your servo go in reverse.