To reproduce:

1. Open attached project.
2. Execute menu item: "BUG/Build Asset Bundles"
3. Open and play scene: MainMenu.
4. Press button "File Default" to load bundles.
5. Press button "Load Scene"
6 (optional). in hierarchy look for any sprites, check sorting layer

Expected result: A game scene should be loaded where you can walk shoot, with obstacles and falling enemies.
Actual result: A game scene is loaded, but only the background is visible. Other sprites are behind it.

This happens because when sprites are loaded from asset bundles, they lose their Sorting Layer value (it is always "Default" for every sprite). When the scene is played directly, it works perfectly fine, Sorting Layers are correct. Open scene "2D" to see that sprites do have Sorting Layers assigned to them.

OR: it might be that Sorting Layer is dropped when building asset bundles.

Not reproducible: 5.6.0a2
Reproducible: 5.6.0b9