When using the rotation tool (W) to rotate a layer, after completing a full lap (360deg) the value resets to 0 instead of 1x+0.0
Once the rotation surpasses 360deg, the value snaps back to 1 lap plus however many degrees rotated.
I encountered it after trying to rotate a layer 360 degrees over time. Since the value resets back to zero no extra keyframe is being set.