To reproduce:

1. Download attached project "stellar-trail copy.zip" and open in Unity
2. Open "MissionDev" Scene
3. In Hierarchy expand Canvas / VehicleAssemblyPanel3
Note: Observe that UIActionButton_Attach is sibling 0 and UIBody_Background is sibling 1
4. Move UIActionButton_Attach lower down the Hierarchy and save the scene.
5. Enter Play mode

Expected Result: Hierarchy stays up the same
Actual Result: In Hierarchy UIActionButton_Attach object returns to the original position

Note: If you will break the prefab that is UIActionButton_Attach and then create a new one, Hierarchy will stay up as it was before the Play mode

Note: Cases 589430 and 668282 are with the same problem, but they were fixed, so there is regression

Reproduced on Unity 2017.1.0f1 and 2017.2.0b1
Could not check on Unity 5.6 because scripts becomes corrupted