I was flying my L39 over the weekend and kept hearing this "tinging" noise. When I pulled it appart for storage, I noticed this crumpling near the end of the pipe on the outer heat shield. Never had it before with my previous plane or any other for that matter.

Crumpling at the end of the exhaust.
The inside of the pipe looks fine with no issues. Also, the airflow is pretty good around the pipe and the distance from the end of the turbine to the straight part of the pipe is 1". Does anyone have any idea what could have caused this? There are less than 10 flights on this bird.
Thanks,
Tone.