Blend Space Deforming Incorrectly - Unwanted Shrinking


I created a simple blend space and I want this chest to do a simple opening animation. However, when I scrub the animation using the blend space bar in the Shape Editor, the model opening its lid will have its lid getting smaller as it opens, and then at the end the lid goes back to its original size.

Do I need to add some sort of constraint to keep this from happening? What do I need to watch out for in order to have maximum control over my blend spaces?

Both models have exactly the same amount of faces and vertices. Please see the video below to see my problem first hand. Thanks for your help!


blendshapes are linear. you need an inbetween.