1. Create a new project
2. Download and import https://www.assetstore.unity3d.com/en/#!/content/59341 project from Asset Store
3. Play "cg2dBoard" scene (doesn't matter for how long. You can play it and after few moves exit playmode)
4. Download and import https://www.assetstore.unity3d.com/en/#!/content/72717 project from Asset Store
5. Play "GamePlay" scene (Assets/Tetris Template/Scenes)
-- Notice that Unity crashes

Regression introduced in 5.5.0b6