Reproduction steps:
1. Open the attached project (New Unity Project 1.zip)
2. Open the "scene.unity" scene.
3. Enter the play mode
4. Observe the objects which are drawn to the right.

Note: the blue object is drawn by the Graphics.DrawMesh method, the red object is drawn by Graphics.DrawMeshInstanced

Expected result: The red object is drawn the same way as the blue object.
Actual result: The part of the red object is not drawn.

Reproduced on: 5.5.0b4, 5.5.0b5, 5.5.0b9, 5.5.0b10 and 5.6.0a1
Note: The method Graphics.DrawMeshInstanced was not implemented on the older version than 5.5, so the bug can be observed only on this version.