Depending on the camera angle and the distance of the animated Objects to the camera they flicked in and out of view.
Since I have no idea what could be causing this and didn't manage to limit the problem other than moving the camera please state what valuable information I should supply.
The Model is parented to a camera which is parented to a character controller. The Animation is undisrupted during scene view. If I move the camera further away from the model, or look in a different direction the models remain visible throughout the entire animation.
I have recordet the incident: https://youtu.be/b66N80_Fg_g
As you can see the right hand, the magazine and at one point even the weapon disappears from view.