Reproducible on:
5.4.2f2
5.4.1f1
5.3.6f1
5.2.5f1

Repro Steps:

1- Download the repro project provided by user.
2- Open the scene in the project.
3- Select three rightmost objects in the scene.
4- From Inspector->Transform, click on the 'S' button next to scale.

Expected Result: Vector3 scale value of selected objects should be set to (1,1,1).
What Happens: Nothing changes.

-Issue doesn't occur if you change the script(TransformInspector) to set the value to something other than (1,1,1).
-Issue only occurs with some combinations of objects, rightmost three is one of those combinations. (3rd and 4th objects from left is another combination)