MP: exception caught with cause com.sap.engine.services.jndi.persistent.exceptions720.Namespac in PI

[#1]

Hello Experts,
We are facing an issue in SAP PI/PO where the message is processed successfully and delivered to the target system, but the sender receives an HTTP 500 error. In the logs we see the following:

MP: exception caught with cause com.sap.engine.services.jndi.persistent.exceptions720.NameNotFoundException: Object not found in lookup of NamespaceMapperBean.

Even though message delivery is successful, this exception still appears and causes the user to see a 500 Internal Server Error.

Could you please advise what could cause this..

Thank you