Cost element & is also used for line ID &

What causes this issue?

Cost element &V1& specified in the currently processed update rule is
aleady being used in the update rule for <DS:GLOS.line_ID>line ID</>
&V2&. The same cost elements cannot be used in different update rules
of a the same valuation method (determined by the values for the
<DS:GLOS.controlling_area>controlling area</>,
<DS:GLOS.results_analysis_version>results analysis version</>, and
<DS:GLOS.results_analysis_key>results analysis key</>).

System Response

The system requires that you enter a cost element which is not being
used in other update rules.

How to fix this error?

Enter a valid cost element that is not being used in another update
rule for the same valuation method.
The cost elements for "cost of sales / revenue" are not displayed In
the maintenance of the update rules in Customizing for work in process.
The cost elements entered there are also used for checking, however. If
necessary use Customizing for Results Analysis. These cost elements are
shown in the update rules for Results Analysis.

Error message extract from SAP system. Copyright SAP SE.