It (always?) comes with replacement parts (they're generally in the same bag with the instructions and a little screwdriver). I only replaced the right shoulder (the weight of the fusion cannon was a bit too much), 1 minute work and it's good to go. You can still quite easily pop off the arm, but with a balljoint you can't expect otherwise... On my copy the replacement shoulder is not too stiff, it's almost perfect. Ymmv.