How to reproduce:
1. Open users attached project and "Scene"
2. Select the "Cube" GameObject and open Animation window
3. Select the frame (0:05 for example), observe that Preview is automatically enabled
4. Right click "Is Trigger" under the Box Collider component (in a "Cube" GameObject) and select Add Key to key it in the animation (the "is Trigger" checkbox should be previously enabled)
5. Disable the Preview mode and exit the Animation window

Expected result: "Is Trigger" boolean property should stay enabled, as it was before keying it into Animation
Actual result: "Is Trigger" boolean property is now disabled

Reproducible with - 2017.1.0a3, 2017.1.1f1, 2017.2.0b10, 2017.3.0a7

Note: The bug only reproduces when adding animatable properties of GameObject by described steps above. It does not reproduce when adding a Property from Animation window itself