Error message when changing the engagement primary expense approver

Symptoms
When changing the primary expense approver, an error message occurs.

Error
The expense approver and the original secondary expense approver cannot be the same person.

Resolution
This message occurs if the resource chosen as primary expense approver is also listed ad 'Original secondary expense approver'. It means, that this resource has delegated the expense approval rights. When the resource ends the delegation, it will become again the secondary expense approver for the engagment. Hence it is not allowed to also select this resource as primary expense approver. Otherwise primary and secondary approver would become the same. A different secondary expense approver needs to be selected.