Child items missing during CO11N

Hi Experts,

We are facing a problem, suppose we have created a bom of one fg, child items are suppose 20 differenet different material code.

When we are confirming the production order co11n (created thru planned order on planning run), we observed that in some cases one /two particular item missing in co11n during confirmation. But actually that item is consumed. When we do read PP data than those items suddenly appear. Nobody have the right of CO02, CO01, CO11N where user can change or delete any line items, we have created z t-code for co11n where line items are greyed out. This problem happens one in 100 production orders.

Now we are not sure which material is not consumed in which production order. What may be the possible cause of this problem.

Regards

Ishu