A User has a script that updates the position of the points of a SpriteShapeController's Spline at runtime. In the Editor, when pressing Play, everything updates accordingly and the Mesh matches the positions. However, when building to Windows, OSX, iOS, Android or WebGL executable, the Mesh does not update after the first frame

To reproduce:

1. Download attached project "soft-shape.zip" and open in Unity
2. Open "Main" scene
3. Enter Play mode
4. Observe that the blue Sprite Shape Mesh deforms to match the positions of the Children with Rigidbody2D components
5. Exit Play mode
6. Build and Run to any platform
7. Run built project

Expected results: You will see hat the blue Sprite Shape Mesh deforms to match the positions of the Children with Rigidbody2D components
Actual results: You will see a static version of the Mesh, but the Rigidbody2Ds will still be moving around as normal, though you won't easily be able to see that in a build without some debug drawing

Notes:
- This issue reproduces on both Windows and OSX Standalone
- This issue reproduces on WebGL, Android, and iOS platforms
- There are no errors or crashes logged out

Reproduced on Unity 2018.1.9f1, 2018.2.0f2 and 2018.3.0a5
Could not reproduce on Unity 2017.1, 2017.2, 2017.3 and 2017.4 because the project becomes corrupted