After editing a destination path, editing motion tween no longer affects whole curve

After editing a destination path, editing motion tween no longer affects
whole curve

I created a motion tween, and at the final frame moved the symbol to its
destination. I was then able to manipulate the curve by dragging the
points, or using the subselection tool to invoke the bezier handles, and
everything looks smooth. However, if I then move the object, even a tiny
bit, future changes to the curve now no longer smoothly affect the whole
curve, but will bend and contort it in tiny subsections, resulting in a
very knotted curve, and the only way to get back there is to undo my way
up the stack to where I dragged the object in the destination frame and
redo my desired curve.
Clicking on the object and moving it is doing something to my editing
mode, but for the life of me I cannot see what it is. Might anyone be able
to tell me what it is, and what I would have to do (I am using Mac OS X
CS6) to return myself to being able to smoothly tweak the whole curve and
not just subsections?