Field '&1' (&2-&3) cannot be changed

What causes this issue?

This field cannot be changed for one of the following reasons:
The shipment status is so advanced that certain changes are no longer
allowed (for example, you cannot change the route once the MRP status
has been set).
You can only enter input in some fields once another field contains a
certain value (for example, it only makes sense to enter a pricing
procedure in the shipment header if the shipment contains costs).
Certain fields for the border crossing and load transfer points are not
ready for input at stage level (for example, distance).

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.