Condition & is not allowed as header condition

What causes this issue?

The condition cannot be entered at header level because it is not
marked in <GL:customizing>Customizing</> as being a header condition.

How to fix this error?

Delete the condition entered from the document header, or mark the
condition as a header condition (in the detail screen of the
<GL:condition_type>condition type</> in Customizing), if necessary.
INCLUDE 'NA_SYSAD3' OBJECT DOKU ID TX LANGUAGE E

Error message extract from SAP system. Copyright SAP SE.