How to reproduce:

1. Open a new project
2. Import attached package
3. Go to Edit/Project Settings/Time
4. Set the FixedTimeStep to 0.002 (10 times less than default)
5. Open scene Scenes/large mass.unity
6. Play the scene
- Note that the large cube falls until it hits the ground and after rolling a bit, begins bouncing uncontrollably
- This does not happen with PCM disabled
- Happens with FixedTimeStep set to 0.02, but easier to see with 0.002

- Reproduced with 5.6.0f2 (3538e0118e7a), 2017.1.0a6 (6ffa0796a506)