The Code engine ejecting out of the body while underpressure is caused by the engine not fully locking in place. Any time you remove the engine and put it back in make sure the button always goes all the way down to fully lock in place. This video shows what to look for: https://www.youtube.com/watch?v=9QPxleJ0Kf8&list=PLQZd_-FISdvjtI5QAsmd6hOTjhd5DEhTI&index=15