The shoulders don't use actual, spring-based ratchet joints. Instead, they use peg-in-a-bracket pseudo-ratchets. And the plastic used for the brackets, which seems to be just the same ABS as the red body pieces, is evidently a tad too rigid to hold up in that job forever:
One bracket had split at both ends, the other had split at one. I glued them and reinforced with cardstock, but I don't know how well it will hold up over time.
It would be nice if someone would produce replacement brackets, ideally metal ones. Better still would be replacement shoulders with real sprung ratchets, but just being able to replace the original brackets with new ones (ideally metal, or at least an engineering plastic that would hold up to the job better) would be acceptable.
