How to reproduce:
1. Create a new project
2. Import the attached "NavMesh_Bug.unitypackage" asset's package
3. Open "JoinedNavMeshScene" scene and play it
4. Click on the NavMesh space on the black cube

Expected result: NavMesh.SamplePosition finds the closest point on NavMesh on the same X-Z plane
Actual result: NavMesh.SamplePosition finds the closest point on NavMesh on the different Y position

Reproducible: 2017.3.0a1, 2017.4.20f1
Can't reproduce: 2018.1.9f2, 2018.3.5f1, 2019.1.0b2, 2019.2.0a2, because of a lot of 'The type or namespace name ... could not be found' errors