Reproduction steps:

1. Open "MinimalRepro.zip" project
2. Open "Level_Apartments" scene
3. Select "Looter" in the Hierarchy window
4. Open the Animator window
5. Select any Animation Transition (e.g. from "Idle" to "Move")
6. In the Inspector window change the Transition name and press "Enter"

Expected Result: The name of the Transition changes after pressing "Enter"
Actual Result: After pressing "Enter" the name doesn't change

Reproduced with: 2017.3.0b4, 2017.2.0f3, 2017.1.2f1(Name changes only after restarting the Editor), 5.6.4f1(Same as 2017.1.2f1), 5.5.5f1(Same as 2017.1.2f1)

Workaround:
Select a different transition and come back to the one that was renamed