Splitting a "sweeped" entity with surfaces not working properly

Hello,

I have an entity, which I wish to split in several entities. 

The object is to be split by the vertical surfaces (attached files). But, when I bake the result, it seems that there are multiple entities generated.

Plus, the corners are not split. 

Is it an error, or I am doing something wrong?

Is there an other way for this ?

Thank you for support,

T.