I also want to add that when it reaches the top, the core shouldn't just stick in place for a few frames. The vertical position should move along an ease in/out curve and stay on its highest only for a single frame.
Second thing, you need
follow through. As the blob goes up, you correctly made some of its mass lag behind. But when the core gets to the top, the gooey stuff around it (that's lagging behind) is still going to move up and take a few frames to stop, overshooting the core.