A 3D object has a sphere collider and is rotating. When its scale changes, the child object starts changing shape and size. This can happen when scale is changed in Play mode or in Edit mode and then switching to Play mode. Also it doesn't matter if scaling is changed when the parent object doesn't have a children object, they can be attached after the scaling has changed and still the issue appears.

How to reproduce:
1. Open QA's attached project
2. Play the scene
3. Select "Cube" and change its scale
4. Observe how the "BigCube" starts changing its shape and size

Expected result: Child cube does not change its shape and size
Actual result: Child cube starts changing shape and size

Reproducible with: 2017.3.0a2, 2017.2.0b6, 2017.1.0p3, 5.6.0f1, 5.5.0f1, 5.4.1f1

Note: In 2017.3.0a2 and 2017.2.0b6 the child cube is rotating along with the father, but still changes in shape and size