To reproduce:
1. Open the user's attached project
2. Play the scene
3. Enable the Frame Debugger, there will be two Dynamic Batches
4. Unpause the Game, use the "Click me" button to change one of the sprite material's shader
5. Enable the Frame Debugger once again
6. Notice there is new additional new Draw Dynamic

Expected result: After changing the sprite material's shader to "Standard" and then back to the original "Sprites/Default" keeps the sprite dynamically batched
Actual result: After changing the sprite material's shader to "Standard" and then back to the original "Sprites/Default" the sprite gets its own dynamic draw call

Reproduced with: 2017.4.11f1, 2018.1.9f1, 2018.2.7f1, 2018.3.0b1