Models keep coliding with each other


I need help on this one.I have a problem with animating object A leaving object B and then object C entering object B.
The thing is when I try key frame first animation everything works fine.But when I try to detach object from other one previous key frame gets screwed up.They are not in sync anymore.Models just keep colliding.I could try and separate this in graph editor but it will take ages even on simple animation like this.

I have done animation in blender file and picture what it should act like.I already tried working with Child Of constraint but same thing or worse happens unless I’m making some mistake here.Same with parenting.

Link to the blend file:

you might have better luck asking this question in the game engine forums…