Item not Fetching for the 2nd Item in the Maintenance Schedule

In the Maintenance Schedule I select the Sales Order for a customer.

Example:-

  1. If the Sales order has 2 items.
  2. I select 1st Item in the Maintenance Schedule.

My clarification is that the system is not fetching the items for the second time if I have to do the Maintenance Schedule for the 2nd item.

Please Clarify on the same.