I've installed a K&S 46/50 muffler on my Raptor 50 V2. It worked fine so far until yesterday. The muffler was suddenly broken while I was having inverted flight tail in circle. I enclosed a few pictures. The muffler was ejected just like a bullet shouted out from a gun.

Why ?

I am using OS 50 Engine and Coolpower 30%. The OS engine was installed only a month ago. The needle setting was one and half turn. Each flight last only 7 - 7.5 minutes. It should not be lean.

What do you think ?