What happens when a motor/esc fails? I have seen nothing showing how the copter is controlled. DJI has a power output fail protection, which allows you to control the copter. It appears Freefly has done a lot of testing, however, a motor/esc will fail at some point. It will be nice to see how the Synapse will react to a motor fail.
Check out this article on the ALTA written by Steve Maller, specifically question #2. Hope this sheds some light on your question http://perspectivair.com/2015/04/15/freefly-alta-first-impressions-and-technical-qa/
It's a good article but does not really confirm what happens. How about redundancy? What if you lose a motor? The Synapse flight controller can compensate for the loss of a motor to a certain degree and you may be able to fly and land safely. Maneuverability is compromised, especially for yaw, but the copter can theoretically fly on 5 motors as long as the payload is not to near the max. Stated another way, this is not perfectly clear at this time." What we need to see is a video showing a motor fail and controllability.