When merging 2 leads using the API, I am getting 611 error code with "Failed to merge leads" as the status.
I understand that this is likely due to a failure on the CRM side, but the result in Marketo is still mind-boggling. The result of this API call is that the surviving record remained and the merged record is no longer in Marketo. However, there is no activity in the surviving record to prove a merge happened. Is this correct behavior?
That is not the correct behavior. Please file a support ticket with the details of your call and the effected records.