There is no way you can tell when the Kinect is finished tilting but you are overseeing one time. MSDN says the following
To reduce wear, your application should change the elevation angle no more than once per second. In addition, you must allow at least 20 seconds of rest after 15 consecutive changes.
So the error can be throw in two situations, either by changing the values to fast after one another or not letting the camera rest after 15 ways.
Just ALWAYS put a try-catch around the getter/setter of the Kinect Angle.