In case of several sched. lines, function only poss. from schedule screen

What causes this issue?

If an item contains schedule lines, you must enter the components
(materials provided to the subcontractor) for each schedule line. You
can thus only perform this function from the schedule screen.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Display the schedule for the item.
Perform the function.

Error message extract from SAP system. Copyright SAP SE.