Blocks and Bad Objects

Hi there.
I´m currently designing a kitchen and I have all the furniture in separated files. Each time I need a model I jus insert it as a BlockInstance in the new file. This Files have some blocks as well, things like, handles, screws, hinges, legs, etc.

I doble click in the block instance of a Drawer to edit it, but by curiosity I executed the SelBadObjects command and Rhino selected the block instances that are inside the main blockinstance (Legs).

Why did Rhino selected Block Instances?

(I wnet back to each file of a part that makes de assembly and they had no errors in any surface)

Can you share the file in question?