Getting "Unexpected character encountered...." upon DownloadZippedDocuments

Hi , Please assist with "Could not download the documents to a zip file. Exception: Unexpected character encountered while parsing value: <. path="" line="" position="" exception.="">Here's the code piece that produces error:

        public void downloadDocument(string packageId) {

            Logger.Info("DOWNLOADDOCUMENT");
            string fileLocation = string.Empty;

            try {
                var eslClient = new EslClient( C.OSS.API_KEY, C.OSS.API_URL);
                var pkgId = new PackageId( packageId);

                Logger.Info("C.OSS.API_KEY: " + C.OSS.API_KEY);
                Logger.Info("C.OSS.API_URL: " + C.OSS.API_URL);

                fileLocation = C.SIGNED_DOCUMENTS_STORAGE_PATH + "\\" + pkgId + "_" + DateTime.Now.ToString("yyyy_MM_dd") + "_" + Guid.NewGuid() + ".zip";
                byte[] content = eslClient.DownloadZippedDocuments( pkgId);

                Logger.Info("FILE SAVE PATH: " + fileLocation);
                File.WriteAllBytes( @fileLocation, content);
            } catch (Exception ex) {
                Logger.Error("EXCEPTION: " + ex.Message);
                Logger.Error("FILE SAVE PATH: " + fileLocation);
                throw;
            }
        }

Here's the trace from the above code: 2019-07-03 09:39:58,810 [10] INFO eSignListener.Controllers.CallbackController - RECEIVED CALLBACK 2019-07-03 09:39:58,857 [10] INFO eSignListener.Controllers.CallbackController - CALLBACK PAYLOAD: { "@class": "com.silanis.esl.packages.event.ESLProcessEvent", "name": "PACKAGE_CREATE", "sessionUser": "FEcgqb15yCME", "packageId": "unXAewAPSBSA5Nt3YZbqudP0ds0=", "message": null, "documentId": null, "createdDate": "2019-07-03T13:39:58.385Z" } 2019-07-03 09:39:58,857 [10] INFO eSignListener.Controllers.CallbackController - PROCESSED POST 2019-07-03 09:40:36,983 [8] INFO eSignListener.Controllers.CallbackController - RECEIVED CALLBACK 2019-07-03 09:40:36,983 [8] INFO eSignListener.Controllers.CallbackController - CALLBACK PAYLOAD: { "@class": "com.silanis.esl.packages.event.ESLProcessEvent", "name": "PACKAGE_COMPLETE", "sessionUser": "FEcgqb15yCME", "packageId": "unXAewAPSBSA5Nt3YZbqudP0ds0=", "message": null, "documentId": null, "createdDate": "2019-07-03T13:40:36.797Z" } 2019-07-03 09:40:36,983 [8] INFO eSignListener.Controllers.CallbackController - PROCESSED POST 2019-07-03 09:40:36,983 [8] INFO eSignListener.OssCallbackHandler - PACKAGE_COMPLETE 2019-07-03 09:40:36,983 [8] INFO eSignListener.OssService - DOWNLOADDOCUMENT 2019-07-03 09:40:36,999 [8] INFO eSignListener.OssService - C.OSS.API_KEY: xxxxxxxxxxxxx== 2019-07-03 09:40:36,999 [8] INFO eSignListener.OssService - C.OSS.API_URL: http://xxxxxx/api 2019-07-03 09:40:37,046 [8] ERROR eSignListener.OssService - EXCEPTION: Could not download the documents to a zip file. Exception: Unexpected character encountered while parsing value: <. path="" line="" position="" error="" esignlistener.ossservice="" file="" save="" path:="" e:="">