1. Create a new project
2. Open the Timeline Editor window
3. Create a new Timleine asset for any gameobject in the hierarchy
4. Create a few keyframes for position
5. Expand the curve editor
6. Attempt to move individual keyframes for curves

Expected result: keyframes move as expected
Actual result: keyframes sometimes lock up in their starting position if a few keyframes are in a vertical line

Reproduced on 2017.1.0b4,2017.1.0b1
Feature introduced in 2017.1.0b1

Notes:
-Sometimes it does not lock up
-Can be moved by changing the keyframe angle