To reproduce:

1. Download attached project "907495.zip" and open in Unity
2. Open "test" scene
3. Zoom in and zoom out in Scene view

Expected result: In Scene view, you will see that shadows are being rendered correctly
Actual result: In Scene view, you will see that shadows are being rendered through the tree

Notes: This Bug occurs if these settings are set:

1. Camera Rendering Path is set to Deferred
2. Directional Light Mode is set to Mixed
3. All Cube's game objects Light Probes are Off and Lightmap Static setting is checked
4. In Lighting settings, Lighting Mode is set to Shadowmask
5. In Quality settings, Shadow Distance is set to 25

Reproduced on Unity 5.6.0b9, 5.6.0b10, 5.6.0p4 and 2017.1.0b4
Not reproduced on Unity 5.6.0b2 (introduction of the shadowmask feature) to 5.6.0b7
Regression on Unity 5.6.0b8