How to reproduce:
1. Open the attached project named "Case_1120471"
2. Change the Sprite of the "Diamond" Tile to the "Circle" Sprite
3. Save the scene
4. Double click to open the "Grid" Prefab

Expected result: Tilemap's Tile has the "Circle" Sprite
Actual result: Tilemap's Tile has the "Diamond" Sprite

Reproducible with - 2018.3.3f1, 2019.1.0b1, 2019.2.0a3
Could not test with - 2017.4

Workaround: User must manually re-enable Tilemap Collider before saving the scene to avoid the issue

Notes:
Changing the Sprite of the Tile breaks the "Grid" Prefab's Tilemap Collider
The breaking of Tilemap Collider is described in the Case 1113092. The issue could be related to that bug.
2017.4 version does not have the new Prefab workflow