Steps to reproduce:

1. Open attached project and open 'Scene.unity' scene
2. Open animator window, start the scene and select 'Cube' game object to observe its animator
3. Notice that Animator gets stuck on two states: 'ThrowAir' and 'ThrowDown'

Expected behavior: Animator doesn't get stuck and ends in 'StandBy' state.

Note: Script attached to 'Cube' sets the animator speed to 0 during the 'ThrowAir -> ThrowDown' transition, which will interrupt the 'ThrowAir -> Throw' transition. When this happens the animator gets stuck at a state of both 'ThrowAir' and 'ThrowDown' is playing, and no other transition does happen.

Reproduced with: 5.2.4f1, 5.3.0p1, 5.4.0a6
Not reproducible: 5.1.4f1