How to reproduce:
1. Open the attached project named "Case_1113092"
2. Turn "Grid" into a Prefab and delete its Instance from the Scene
3. Change the Sprite of the "Diamond" Tile to the "Circle" Sprite
4. Double click to open the "Grid" Prefab

Expected result: Tilemap Collider matches the outline of the new Sprite
Actual result: Tilemap Collider does not match the new Sprite

Reproducible with - 2018.3.3f1, 2019.1.0b1, 2019.2.0a2
Could not test with - 2017.4

Workaround: User must manually re-enable Tilemap Collider for it to match the new Sprite

Notes:
Tilemap Sprites and Collider does update when the object is in the Hierarchy but does not update automatically in the Prefab mode
Prefab's Instances have the correct Collider
2017.4 version does not have the new Prefab workflow