Articles are still assigned to layout module &1

What causes this issue?

Materials are still assigned to at least one version of the layout
module. Only the current version and possible future version are to be
taken into consideration.

System Response

It is not yet possible to delete the selected layout modules.

How to fix this error?

Delete all material assignments to this layout module using
<DS:TRANS.MM42>integrated material maintenance</>. To do this, call the
basic data view for the articles concerned and navigate to the
additional data for the layout module information. You can delete the
field entries for the relevan layout modules here. You can get an
overview of which articles are contained in the relevant layout modules
by calling the layout workbench (transaction: <DS:TRAN.WLWB>WLWB</>)
for a customer to whom you have assigned a layout module. Choose the
pushbutton for the version and you get an overview which contains all
materials.

Error message extract from SAP system. Copyright SAP SE.