How to reproduce:
1. Download, extract and open user's attached project (Character Controller Glitch.zip)
2. Open 'SampleScene'
3. Enter Play mode
4. Walk around the bars in front of the Character Controller

Expected results: Collision happens as long as the Character Controller is moving towards the bars
Actual results: Approaching the bars from some angles make the Character Controller stuck and unable to move, along with an error that says "transform.positionWithLocalOffset assign attempt for 'Name' is not valid. Input positionWithLocalOffset is { NaN, NaN, NaN }.
UnityEngine.CharacterController:Move(Vector3)"

Reproducible in: 2018.1.0a6, 2018.1.9f2, 2018.2.17f1
Not reproducible in: 2017.3.1p4, 2017.4.16f1, 2018.1.0a5

Note: Could not test in later versions (2018.3 and 2019.1) because the moving script in the example project is written in UnityScript, which does not work in 2018.3 and onwards.
Note 2: Opening the project in earlier versions, the bars in the example project will become Missing Prefab's. To reproduce the bug, one should create one or more shapes with a Convex Mesh Collider with a Cylinder mesh.