How to reproduce:
1. Open the user's attached project
2. Open scene Scenes/SampleScene
3. In the Project window, select the Prefab Asset "TestTilemap", and select Open Prefab in the Inspector view
4. Go to Window -> 2D -> Tile Palette
5. In the Tile Palette window, select TerrainPalette from the drop-down menu, and set the Active Brush to Custom Default Brush
6. Uncheck the Auto Save box at the top of the Scene view
7. Modify the Terrain Tilemap
8. Click the Save button and return to observe the Scene by pressing "Scenes" at the top of the Scene view
9. Repeat steps 7-8 several times after returning to edit the Prefab

Expected result: the Tilemap in the Scene is consistent with the changes made to the Prefab
Actual result: the Tilemap is inconsistent between the Scene and the Prefab, Sprites change and overlap unpredictably

Reproducible with: 1.0.0 (2021.1.27f1, 2021.2.0b17, 2022.1.0a13)
Could not test with: 1.0.0 (2019.4.32f1, 2020.3.21f1) (the user's project breaks after downgrading)