Thanks for the file, and for using DropBox.
Could it be that the refresh of the Editor view, which is constant updates, will lead the Spring Constraint to move?
Since the editor view is not a reliable source for priorities or processes that update/change over “real” time (vs. scene time).
Press play and stop at any time. Now press shortly the a key. … and again. Now hold the a key down. See what happens? Is that the “delay” you are seeing?
The only way to fix that is to select the Null that is constrained to the Spring, call up Cappucino, and “bake” the movement of the Spring influence, then switch the Spring off.
By the way, if you use the five Null Objects in a MoGraph Tracer> Connect all Objects, while in B-Spline mode (Uniform Intermedia points, e.g., 24), you do not need to the Spline IK. You get the same result.
All the best
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