Weird drop zone behavior when animating the crop parameter.

I'm animating a drop zone so it starts with it's sides cropped in. Then I have the left and ride sides uncrop to zero.

When I animate back to zero, the left side does not go back to its original position. I.e. to the edge of the video frame.

You can see the drop zone before it's cropped in the image named Start Crop.

You can see the crop in the image named Cropped.

You can see the error/ bug? in the the image named Weird Behavior.

I can only see the one image, "cropped."
I have various issues trying to animate drop zones. These problems have been around as long as drop zones have so I basically stopped using them. I figured I just didn't get it. But I'm starting a series of short programs where drop zones are going to be critical to efficiently building stylized segments that just have content changes.
Sorry not be able to add anything helpful but I'll drop back in a few days after waging my own drop one battles and let you know how they turn out.