The pitch servo is frozen in place. I removed it from the airplane and used a servo tester, and nothing - no movement at all. I can't even move the servo manually by pushing on or turning the control arm.
While it's possible that this happened at impact, we have concluded that the pitch servo failed by just freezing in place - at the most inopportune time. We think the pitch servo simply froze with the elevator in a neutral position as it was at around 4:09.5... never to respond to signal again. Perhaps we've learned our lesson on using cheap Tower Pro SG90 9g servos.
Picture here These days we're building with foamcore and hotglue, it's cheap, light, strong and quick to build. 2-3 hours build time for this aircraft.