jaydisc is correct. Ever since late G2 (and popularised during Beast Wars) Transformers have featured parts that are intentionally designed to pop off under stress, as opposed to say old G1 Transformers where parts would just break off under stress. Some of the early BW toys featured parts that fell off a bit too easily (e.g.: Basic Optimus Primal, and remembering that this was 12 years ago) but they've improved on that. I agree that some toys still feature parts that pop off a bit too easily (like on some Star Wars Transformers) - but that would be more of a design issue, not a QC issue.

A QC issue would be say the face of my Cybertron Ransack... a quarter of his face is unpainted so he has this big red splotch on his face. That's not a design flaw, that's just bad QC!