Non-Boolean value & in HIDEFLAG of the included search help &

What causes this issue?

Field HIDEFLAG of a search help inclusion contains a non-boolean value
(that is, a value which is neither ' ' nor 'X').

System Response

The action is terminated.

How to fix this error?

Make sure that the Dictionary sources of the search help are
consistent.

Error message extract from SAP system. Copyright SAP SE.