Product/Backend metric method ref for mapping rule not found

Issue

• When updating the methods and mapping rules in the Backend CR the following error is shown:
  Error sync backend [backend-name] mappingrules: backend metric method ref for mapping rule not found
• When updating the methods and mapping rules in the Product CR the following error is shown:
  Error sync product [product-name] mappingrules: product metric method ref for mapping rule not found