Steps to reproduce:

1) Download attached project and open in Unity
2) Open 'Test' scene
3) Click on 'Ethan' gameObject in Hierarchy window
4) Press Play
5) Press on GUI.Button 'AOC2 Clip' in Game view
Animation Controller will be switched to AnimatorOverrideController 'OverRide_Full' (Check Inspector window >> Animator component)
6) Press on GUI.Button 'AOC1 Clip'
AnimatorOverrideController 'OverRide_Full' will be switched to 'OverRide_Alt' AnimatorOverrideController and animation will freeze (check Inspector window >> Animator component)

Expected result: Switching between AnimatorOverrideControllers should not freeze animation (check attached gif 'noRepro.gif')
Actual result: Switching between AnimatorOverrideControllers makes animation to freeze (check attached gif 'repro.gif')

Reproduced with:
5.6.0b11, 5.6.1p1, 2017.1.0b5

Not reproduced with:
5.5.3p3, 5.6.0b10

Regression from: 5.6.0b11