Steps to reproduce:
1. Open attached project in 5.4.0f3 at first.
2. Open "main" scene.
3. Start play mode.
- After 40 seconds "Cube" will start moving fast enough to draw a line(so you could track his behavior).

Problem: Using transform.position for moving child object makes parent object change its position as well.

Expected result: parent object should not move when the child object is changing its position.

I have attached the project which reproduces the issue.

Reproduced on: 5.4.0f3 , 5.3.5p7
Not reproduced: 5.2.3p3