Okay, the problem was that you used bend and swing (or y- and z-rotation) at the same time on the shoulder. That's generally not a good idea, and it won't do you any good when you want the arm to point more or less forward. Instead, use just swing. If you want to rotate the arm up or down a bit from the forward position, use a collar twist for that.

Attached is a partial pose that fixes the problem with the left shoulder, and which I tried to get as close to your original as possible. I'm doing a before-after render at the moment and will post that once it's done.

-- I'm not mad at you, just Westphalian.