Crazy random Movements [Cinema 4D Animation Problem]

I have character which i try to animate its arm. i key framed the arm in first frame and last frame in different positions and and also in between position but it has copmletly random movements. its arm jumps in different positions when i refresh the frame pressing 'a' key. i can see the animation path but it doesn't fallow the path, stops in the middle and does small random movements when i play the animation.

Why does it behave like this? Any suggestion?

cinema 4d r14.042
Windows 7 64x