This bug is similar to case 280936 and a video of the repro steps has been attached. The reason this hurts is because if I am tweaking a single keyframe and testing it out in the game, I have to:
Click Animation Tab
Click on the Keyframe
Click the Record button
Click on the value (or drag the keyframe at this point)
Type in the new value

instead of simply:
Click Animation Tab
Press Enter (or drag the keyframe at this point
Type in the new value

Saving a few seconds like this every time I test the animation means I save hours on a project.