AutoCreate Final Assembly Orders, some sales order line cannot generate WO

Hi Experts

In 11.5.10.

1. Create Sales order for ATO item with multiple lines , same request date and schedule ship date, book.

2. Go to WIP>Discrete , scheduld  AutoCreate Final Assembly Orders with parameters: sales order:null ; offset days: 30 ; load type: Both configured and non-configured Orders; status: Unrelease; org: not null ; classe code: null

3. Sometimes , for same sales order , some lines cannot create WO; when resubmit the program AutoCreate Final Assembly Orders with sales order entered , the sales order lines will create WO.

This issue occur sometimes, but cannot reproduce.

What's reason cause this issue?

Regards

Fengling