ok now that we are on the subject of golf... here i put some lines in to show you what's going on.. your arm is fine. you have the same problem i had... you reverse pivot.
see below. try to keep your head still looking down it can move back behind the ball but never should you be looking to the side or have it with a tilt.. your hips from turing into a U. Turn your arms and your shoulders to rotate..
Everything I say is in my own opinion do not buy sell or hold based off what I have to say.