Reproduction steps:
1. Open the attached project;
2. Open the scene "1";
3. Press Ctrl + Shift + D (CinemaDirector will open);
4. Click Play button in the CinemaDirector window;

Actual result: Unity crashes in mecanim::statemachine::StartState (in about 12 second).
Expected result: Unity shouldn't crash.

Note: I find out that the crash is caused by Mecanim Track Animators Transition Duration and the blue line which represents animation end (blue_line.jpg). When Animators Transition Duration is not enough until it reaches the blue line, Unity crashes. Also, if the blue line is set to time before Animators finish their duration, it also causes the crash.
Furthermore, Unity doesn't crash, if after click Play button in the CinemaDirector window, Unity loses the focus (turn on the other program or a browser).

Reproduced with: 5.4.0a2, 5.4.2f2, 5.5.0f3, 5.6.0b3.
Not reproducible: 5.2.5f1, 5.3.6p4
Regression introduced in 5.4.0