I am a student studying the Compton Camera using MCNP6, but when I code and simulate it with MCNP6, the reactions required for the Compton Camera (Compton scattering (-1) with event number 4000 and photoelectric effect (-3) with event number 4000 occur in succession and then terminate) do not occur. The Compton scattering and photoelectric effect must occur with one other event in between. Can you tell me what is wrong with my code? Or do I need to condition the filtered reactions differently for use in the compton camera?

I've attached my MCNP6 code file.