The Call ambiguous and matches multiple workflow

I have a workflow triggered by an HttpEndpoint that sets a variable and correlation ID using the RequestId from the POST JSON data.
Subsequently, a switch flow determines the path. Under certain conditions, a non-starting HttpEndpoint suspends the workflow, awaiting an "Approve" or "Reject" command posted to the endpoint using the RequestId (CorrelationID).
This simulates a Bookmarked Activity.
The issue is that when two workflows are suspended, the error "The Call ambiguous and matches multiple workflow" occurs. How can I handle multiple suspended workflow instances for a single HttpEndpoint to avoid this error? The error message includes workflowinstanceids like "h5df57f255ddf" and "g5gh57484556".