g18c lever alignment pin is loose?

[Returner]

Hi, Newbie newbz here! Any help would be mucho appricated.
I've just bought a KWA glock 18c and ive pulled off a few rounds on both single shot and auto, i reloaded and started off again in full auto and the lever alignment pin flew out and into my chest?
1. Why?
2. This will go back in but its loose, is it meant to be or does something hold it in place.

Any help would be much appricated.
all the best
Lee