Debri from DM going inside his main DM bugging it

Hi guys,

I have been facing a problem related to debris going inside my main DM.
This DM represents a building that might get some hole made by missiles, I am using a DM whose Support Depth has been set to 1 in order to make possible for making this holes on it.

It is working fine most of the time, the missile hits the building making a hole in the middle of it, what creates a waterfall of debris from this hole until all this lose debris fall. The problem is that in like 5% of this missile hits, one of this debris seams to go inside the main DM, making the big DM just start to shake hard and float a little moving around the scenario until it expel the debri inside it and finally stooping shaking.

Does anyone have any idea how to avoid letting a debri going inside the DM? Or how to identify such debri via code for deleting it?

Thank you.