fcurve madness

When fixing animation always remember to double check fcurves. Two things have recently driven me mad!

(a) on curves using spline interpolation if 2 keyframes are of the same value make sure that you use plateau slopes so that the value between the 2 keyframes does not exceed the 2 keyframes;

(b) if you retime animation make sure that there are no keyframes that are not on frames -- this can be achieved by selecting the keyframes and choosing "move keys to nearest frames". However, this may not work IF there is already a keyframe on the nearest frame and you may end up with a keyframe immediately before or after... if you're working in the dopesheet you won't see this stray keyframe

So the lesson of the day is, if you have movement where you don't expect there to be movement, double check the fcurves for the slope between frames and for extra keys between frames.