This can occur when an application program goes away (primarily a manager application), or an Association/Session is aborted and one of the partners doesn't realize it yet. The response is sent and the invoke id is cleaned up locally, then the partner rejects the message back because the partner is not present. When the invoke id is looked up, it cannot be found. The condition is logged and the message is ignored (no further processing is possible). CMIP services will continue processing.