To reproduce:
1. Create a new project.
2. Create "Particle System" and "Cube" (or any other 3d object).
3. Select "Particle System" enable it's Collision module, and add "Cube" to the Collision->Planes (in that particle system).
4. Select that "Cube" in the Scene view, by clicking on "Cube" where it's "Pivot Point" is.

Expected result: You select "Cube".
Actual result: "Particle System" is still selected, Pivot Point of the cube is displayed, can't move object now. After re-selecting "Particle System" (from hierarchy) it can't be moved or rotated in SceneView, "Cube" moves/rotates instead.

Reproducible: 5.3.7p1, 5.4.3f1, 5.5.0f3, 5.6.0b5

Workaround:
Select objects in hierarchy.
Or After selecting ParticleSystem, try not to select it's CollisionPlane object, by it's pivot point.