Material subject to serial number not possible for external warehouse

What causes this issue?

It is currently not possible to make postings for materials that
require serial numbers when they are managed in external
<GL:warehouse_number>warehouse numbers</>.

System Response

How to fix this error?

Manage the stock in a storage location that is not managed in an
external warehouse number.

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

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.