We have code which we are executing from custom workflow. We are qualifying Lead to Contact, this is working perfectly fine for 80% of transaction but 20% of transaction is not working correctly.
Lead is getting qualified bu contact is not getting created. 

If there is code issue it should failed for all, if security role issue it should fail for all. 

var req = new QualifyLeadRequest
CreateContact = true,
SourceCampaignId = lead.GetAttributeValue<EntityReference>("campaignid"),
Status = new OptionSetValue((int)DGS.RMM.XRM.lead_statuscode.Qualified),
LeadId = new EntityReference(DGS.RMM.XRM.Lead.EntityLogicalName, entityid)

resp = (QualifyLeadResponse)service.Execute(req);

Any comments to find cause will be much helpful.