The substruction will add part of the cutting mesh to final results, seems to related face overlapping when excute substruction

[Qiming0303]

I was using a lot of cuboid to cut a prism, the cutting(substruction) was performed one by one. But at some point, the substruction start to add reundant faces into the outcome mesh. looks like, when the cutting mesh overlap with the target mesh, this happen.

I have tried to add a small movement (0.001f) to avoid this, but it dosen't work. Dose anyone have some suggestion for me about how to get a better substruction outcome?