Loose engine very likey. Or perhaps your cabanes were getting loose as well? If you look at the screw holes and cabane joints you should be able to see if the damage is recent or if it occured over time. I'll bet the engine was bouncing around in there moving the thrust line round by 4 or 5 degrees or more. Stuff like that could cause it. Did you not notice any flopping around of the engine during starting it?

Also next time when something like this happens the FIRST time it's wiser and safer for all persons and property to throttle back and land pronto and give the model a very close inspection. If you'd done that it's likely you would have avoided even the minimal damage. Folks have even avoided a total crash by landing to find loose hinges and stuff that would have caused a complete write off if they had stayed in the air to "test" it.