I was playing with my activator Grimmy last night, and was transforming him to robot mode. As I rotated the wrist so the hands looked correct, I heard a tiny click. A cursory inspection didn't show a problem, so I did the same to the left hand, and was rewarded with another slight click.
Closer inspection of the underside of the arm revealed that the thinner plastic of the ball joint had cracked right through in both wrists. Apparently some genius at Hasbro quality control didn't catch the fact that the either the ball is too big or the socket is too small. Every time it is rotated, the crack gapes wide open, which would almost make it seem as if the ball is irregularly shaped.
I don't know if this is the case with the new Lava Grimlock activator, but I'm not going to take the chance.
Now I gotta hunt down a replacement.