How to split brep with multiple box

Hello. Please understand because I am not good at English.
What I’m going to do is make a bounding box for the model, fill it with a small box, and split the model into small pieces. However, the final result seems to be good in the model I made, but there is an error. If you look at the picture, there is a part where there is no piece. How should I solve this? (17.4 KB)