scene color not working properly when I fiddle with screen position mode

Hi,

Procedure

I was making a tutorial the other day on using screen position and screen color. I began by explaining the various modes for screen position, plugging them into the custom lighting to show the result. After some fiddling, I added a scene color node and plugged the screen position (mode sceen UVs).

Expected result: the scene color should sample everything that's behind my object

Actual result: only the skybox is sampled

From there on, the shader seems to be in a corrupted state. But if I create a new shader and then create a Screen Pos (scene UVs) and directly plug it into the scene color node without playing around with it, it works.

You can see this in action in my tutorial video at 10:30

I've had this occur 100% of the time, doing the exact same steps as on the video

SF version: 1.25

Unity version : 5.2.3f1

OS version: OSX 10.11.2