Problem with API 21

Ok i will try to be clear! when i compile my game with api 21 it crash in android kit kat, i dont know why, but the funny part is that if i compile the game with the pre built lib that comes with cocos installer with api 21 it does not crash… my question is why? there is a problem with this api level?

Im using cocos 3.10 and ndk r10e