The calls may not be duplicates. They can be a conference calls. which have the same SessionID, Session Sequence Number, but different talk time because different agents participated in the same call. (TheDetailed Call, CSQ, Agent Report shows the names of agents who participated in a conference call.)
Another possibility for the duplication that could be explored. Call is sent to one agent, but agent does not answer, so call is sent to second agent (explains zero talk time on one agent).