The title alone here is hard enough work! This was the first time I had ever received a Gundam figure to repair. The process was interesting as I had to make sure the arm fit flush while retaining it’s original articulation. This usually isn’t really a big deal, but the arm is in 3 main pieces. After an attempt or two it dawned on me just how simple the fix could be. I basically grabbed and old Marvel Legends ankle disc/peg and shaved it down enough to fit in the shoulder joint. I also dremeled the shoulder joint’s hole a little larger to give it more mobility. After making sure the peg fit and could swivel, I removed it and drilled a tiny hole through the peg and then inserted a straightened Eye screw. I then proceeded to insert that sharp screw end into the forearm joint. I had also drilled a small hole in the forearm in order for the peg to be inserted tightly. The elbow armor also had to be in place before inserting the peg, so I basically had one shot at this. It worked as planned. You can see the steps I took in the photos below. I hope this helped and I am always here to repair for your figures!