Here is something to consider providing it hasn’t already been covered. Perchance there was undetected damage within the fin that caused the separation or worked in concert with the excessive rudder movement.
Here is a case in point. During the production of the 767, which also has a composite fin an operator of an overhead gantry crane was moving a production jig. He noted that the jig made a very small contact with the fin with that contact being concentrated in a very small area.
He notified the production manager and they sent a technician up to check the contact spot. He returned to ground level and told the production manager that the damage could be worked out with wet and dry sandpaper. They were ready to let it pass when a production technician who specialized in composite repair walked up and indicated that he would go up inside the fin and check it out. What he found were several skin stiffeners that were debonded indicating that the skin oil canned inward about twelve inches and popped out again. They had to remove the fin in an out of position operation and replace it with a newly minted fin assembly. Had the technician not gone up inside the fin then perchance there would have been a 767 that would have lost its’ rudder and fin.
Composite material is very difficult to verify that repairs have been effected properly because in many cases the repair material is opaque to X-ray inspection.