Combination TDP/Oil BOM header and HPM/Oil BOM components not allowed

What causes this issue?

A bill of material was created for an oil product (Oil BOM). But the
oil product (BOM) contains a header material, and in the oil-specific
view in the material master, only excise duty fields have been
maintained. The oil-specific view should match that which is in the BOM
header material.
In addition, the header material does not have an assigned conversion
group, but a conversion group has been entered for at least one of the
components in the oil-specific view in the material master.

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?

Structure the BOM in such a way that if there are one or more
component materials which have a conversion group assigned, the header
material will also have an assigned conversion group.

Error message extract from SAP system. Copyright SAP SE.