Steps to reproduce:

1. Open the attached project
2. Open 'Main' scene
3. Double-click 'Run Controller' asset to open in in an Animator window
4. Play the scene
5. Select 'veteran' game object
6. Stop the scene
7. Notice Animator Window is emptied and does not show the previously opened 'Run Cocntroller'. Try to open any other animator controller after that, notice it does not work.

Notes: Does not occur if the animator controller is simply attached to the animator component on the game object (instead of using runtime animator controller). Can be workarounded by closing and reopening the Animator window.