I'm no expert with pattern planes, but two things stand out to me. One, those rib notches look really deep, almost halfway through the leading edge. And two, the TE break right in front of the horn along with the pushrod being forced out of the servo arm leads me to wonder if counterbalancing the elevator would take some stress off the linkage setup.

Could be that forces on the elevator prevented the pushrod from moving and the resulting compression between the horn and the arm snapped the TE and popped out the pushrod and then the LE broke at its weakest point being the rib notch as a result.