How to reproduce:
1. Open users attached project and "testScene"
2. Open the Game view, notice that there are two White bars in the scene. "TestShader" for them is written in a way that the length of the bar reflects to their material _Color.a value. The top bar's color value was set in its material inspector without animation (to 0.5).
3. Second bar and its Materials Alpha value is not set trough Material inspector and is instead set trough Animation (Material uses the same "TestShader")
4. Enter playmode for Animation to occur

Expected result: Top and bottom bars are the same length
Actual result: Bottom bar is not the same length as the top bar. You can see in the console output that even though the Material alpha values should be equal, the returned Material alpha value is down to 0.2

Note: Reproducible in Linear color space, not reproducible in Gamma color space

Regression introduced in - 5.6.1p1
Reproducible with - 2017.3.0a1, 2017.2.0b4, 2017.1.0p2, 5.6.2p4, 5.6.1p1
Not reproducible with - 5.6.1f1

Fixed in 2017.3.0b1, 2017.2.0f1, 2017.1.1p3, 5.6.3p4