Shipment costs calculation for &. stage has already started

What causes this issue?

You changed the document. This change may be relevant for calculating
the shipment costs.
However, the system already started to calculate the shipment costs. As
a result, inconsistencies may occur.

System Response

In this case, the system issues a warning.

How to fix this error?

Check whether the shipment costs have to be calculated again.

Error message extract from SAP system. Copyright SAP SE.