Heya,
rotations are based off the piot point, and since your not keyframing the pivot point position its just keep the last place you moved it to and using that with your old animation.

Go into the channel editor and click edit>channel control, you need to move the:
rotatePivotX
rotatePivotY
rotatePivotZ
rotatePivotTranslateX
rotatePivotTranslateY
rotatePivotTranslateZ

to your hidden keyable or not-hidden keyable section.

You can now key the pivot freely, the reason this is not keyable by default is to stop artists breaking rigs and setups.