Double placement: layout module &, shelf section &, and shelf space &

What causes this issue?

You have entered an assignment of a material and of a unit of measure
to a layout module. This assignment positions the material on a shelf
space that is already occupied by another material.

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?

Compare the entries in layout module, version, variant, shelf section,
and sort sequence number with other existing entries that are identical
in these fields, but that differ in material and/or unit of measure.
You will find at least one other entry. To ensure unique shelf section
placements, change the duplicate data in at least one of these fields,
or delete the entry.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.