3514037 - Actions in SBPA fail with status code 503

When a destination with authentication type Principal Propagation is being used within an Action in and this Action is used within a process in SBPA, it fails with:
"Action 'action-id' failed with the following error: 'Error thrown from action runtime library: Could not fetch X-CSRF token for action 'action-name': Request failed with status code 503'."

SAP Build Process Automation.

action, runtime, 503, X-CSRF token, user token, principal propagation, api trigger, destination, authentication. , KBA , BPI-PA-RT , SBPA Runtimes(Action RT, Mail RT, Destination-Auth,Mapping) , Problem