Yeh, no screws in torso/shoulder assembly. Only pins.

And honestly, I've looked and looked and I can't see any difference between the working one and the non-working one. However, due to the construction, you can't get a clear view of the 'stop tab' that prevents the shoulder from going past 90degrees. Only way to get a look at that bit would be to push the pin out and disassemble the shoulder.
Not keen on that...