How to reproduce:

1. Open attached project
2. Open scene Scenes/BakedPlane.unity
3. Open the Navigation window
4. Play the scene
- Scene contains a sphere that responds to Arrow Key inputs
5. Try to move the scene around in the Game View
- Note that the sphere moves everywhere except for where the seam is in the NavMesh

- Reproduced in 2017.1.0b5 (e2f219641e2c)
- Present since 5.0

Fixed in 2017.1.0b8