WIP or scrap calculation for parallel operation sequences not possible

What causes this issue?

If the routing specifies a sequence of operations that are defined as a
parallel sequence, this will have the following effects:
The system cannot interpret the confirmed scrap quantities in cumulative
and periodic settlement when it calculates the scrap.
The system cannot calculate work in process (WIP) at target costs for
this order because it does not recognize the relevant operations.

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?

If you want to calculate scrap or WIP, do not define parallel sequences.

Error message extract from SAP system. Copyright SAP SE.