I got my HTS Sideswipe a couple weeks ago and whenever I transformed him, his arms would pop off rather easily. Soo I grabbed my Sunstreaker and after a bit of force popped his arms off and noticed a very BIG differance. The slot that shoulder connects into on the arm. On Sustreaker the slot edges are cut at an angle to match where it connects to the shoulder which if you notice has an angle cut to it as well. On Sideswipe the shoulder connector has an angle around the connection knob but the arm slot is cut flat making it not connect flush. I thought this was a fluke so I bough a second Sideswipe at Walmart last night and it was the same. Its hard to explain but if anyone is having the same issue, pop the arms off the brothers and look at the slots on the top of the arms and you will see. Now im going to either do some cutting on Sideswipes arms or gank the upper arms peices from Sunstreaker when I upgrade to a Henkei Sunstreaker.