Why can't I duplicate then re-assign a BOM?

I have many products that share similar BOMs. Instead of re-writing the BOM, I take one that is similar enough, duplicate it, change it's product, then make the necessary changes to the BOM. When I view the resulting product and it's BOM everything looks ok. But, there are problems in how BOMs link to each other.

• The BOM sturcture is broken. I view the BOM sturcture, tree mode, and it terminates at a product but that product has a BOM so the branch should continue into that BOM.

• When I list the BOM names, I see a lot of left over BOMs with the "(copy)" snippet in their name even though every time I duplicated a Product, I removed that snippet. To view this list, go to Menu: Bill of Materials Components, then filter BOMs with part of the BOMs name.

The solution to this problem must lie in an explanation of the underlying data structure that leads to the solution to this other question:

https://accounts.openerp.com/forum/Help-1/question/28105?answer=28106#post-id-28106

When I duplicate a Product and that Product has a BOM, I get a "Product (copy)" without a BOM. But, is there a pointer to a BOM, a non-existing BOM, that gets copied along?