MacBook Pro (Retina, 15-inch, Late 2013)
NVIDIA GeForce GT 750M 2048 MB
Broken: Version 2.76 (2.76, 2015-Oct-11)
When trying to animate the opacity of a strip in the VSE, once a keyframe is set I can't edit the value in the Properties panel.
**Exact steps for others to reproduce the error**
1. New Blender File (or load attached one)
2. Go to the VSE
3. Add a scene strip
4. Select scene strip with RMB
5. Open up the properties panel with "n"
6. Find the Strip Opacity attribute
7. Drag the opacity.. it works fine.
8. Set the opacity to 0.
9. Set a key by hitting "i"
10. Scrub ahead a few frames.
11. Drag the opacity - It will keep snapping back to 0. Even typing will set it back to 0.