Originally Posted by
MEEEGGGAAATTTRRROOONNN!!!
Something like missing wheels or ladders or wrong pile drivers are pretty easy to address, but things like shoddy chrome (Hot Rod, Ironhide), paint flaking during transformation (Ratchet, Megatron, all the BW figures), mis-assembly and misalignment of parts (Ratchet/Ironhide, Ramjet), are harder to fix.
In the case of Dinobot, the shoulder problem seems in part due to poor design (and possibly material choice). That would explain why Takara is unwilling to offer parts because they're only going to break again.