1. Download user's attached project "FollowPlayerNavMesh.zip"
2. In the project, open the scene "ZombieChaser"
3. Go to Window->AI->Navigation
4. Open Navmesh baking settings window
5. In the Scene view find the stairs as shown in the attached picture and then in "Navmesh bake Settings" try changing "Step Height" value from 0 to 1.2

Expected result: There shouldn't be any gaps created when changing "Step Height" value from 0.76 to 1.08 in the Navmesh baking settings
Actual result: Notice that when changing "Step Height" value from 0.76 to 1.08, there seemed to be a small gap in the default NavMesh going up the stairs.

Reproducible with: 2017.4.10f1, 2018.1.9f2, 2018.2.6f1, 2018.3.0a10

Note: Sometimes NavMesh just disappears when setting "Step Height" value from 0.76 to 1.08 and then baking