Wrong Availability check for Header Item in Sales BOM after BOP

Hi Guys

I am stuck with a very weird problem. Request your advice:

I have a Sales BOM with one item Lets header is 'A' and Item 'B'. On creation of Sales Order ATP check is performed and both the line items (with A and B) the committed qty and committed date.

Now when BOP runs, it deletes the allocation of A and changes it to '0'

Details:

'A' is a non stockable product

Req:

1. I am not sure whether I should include A in BOP selection, however even running it only with B it deletes the allocation of A and the committed qty changes to '0'

Can you please suggest the solution or standard way of running BOP for Sales BOM

Thanks in advance

-Rahul