Item ledger vs Item partlist

Dear Expert,

When users does material issues and completion, it will insert data in F4111 and F3111.

In F4111 insert data with minus amount, in F3111 insert data with positive amount. After Manufacturing Journal Entry, it will insert data in F0911.

But, sometimes there's no row in F3111. It will make variance.

Any ideas how to avoid this case? And how does this case can be happen?

Sincerely,

Oviedityanto