>>6061450I had the exact same issue on my Kickback. It's the same peg on the back piece being too long. Guess it's more widespread than I thought.
If you want it lock, add material to areas circled, that edge on the chest piece and a small nub on the rotating purple piece.
I used applied thin layers of super glue using a toothpick then hardened it instantly using baking soda, tested the fit, repeated until it felt right.
