Reproduction steps:
1. Open the attached project 'Rotate'
2. Open the available scene
3. Rotate the objects 1-6 in the scene view and observe their positions

Result: The transform positions of objects "1", "4" and "5" change when they are being rotated.

When the average transform position of all the object's children is different that the parent's transform position, this effect occurs.

Reproduced with: 5.5.0a2, 5.4.0b25, 5.3.5p7, 5.2.3p3