Error while adding document to existing package.

Team We are experiencing intermittent issue while adding document to existing package. Please let us know why this could happen. For reference i will put in package on which we faced this exception. Upon retry, this is not happening. Details: PackageId: ez60Idp_AXuzPDZV9WSHoksl0X4= Exception: "Silanis.ESL.SDK.EslServerException: Could not send the package. Exception: The remote server returned an error: (500) Internal Server Error. HTTP POST on URI https://sandbox.esignlive.com/api/packages/ez60Idp_AXuzPDZV9WSHoksl0X4=. Optional details: { \"technical\":\"EsepCommand failed and no fallback available.\", \"messageKey\":\"error.internal.default\", \"message\":\"Unexpected error. We apologize for any inconvenience this may have caused you, please try again. If the problem persists, please contact our support team.\", \"code\":500, \"name\":\"Unhandled Server Error\" } ---> Silanis.ESL.SDK.EslServerException: The remote server returned an error: (500) Internal Server Error. HTTP POST on URI https://sandbox.esignlive.com/api/packages/ez60Idp_AXuzPDZV9WSHoksl0X4=. Optional details: { \"technical\":\"EsepCommand failed and no fallback available.\", \"messageKey\":\"error.internal.default\", \"message\":\"Unexpected error. We apologize for any inconvenience this may have caused you, please try again. If the problem persists, please contact our support team.\", \"code\":500, \"name\":\"Unhandled Server Error\" } ---> System.Net.WebException: The remote server returned an error: (500) Internal Server Error.\r\n at System.Net.HttpWebRequest.GetResponse()\r\n at Silanis.ESL.SDK.Internal.HttpMethods.PostHttp(String apiToken, String path, Byte[] content)\r\n --- End of inner exception stack trace ---\r\n at Silanis.ESL.SDK.Internal.HttpMethods.PostHttp(String apiToken, String path, Byte[] content)\r\n at Silanis.ESL.SDK.RestClient.Post(String path, String jsonPayload)\r\n at Silanis.ESL.SDK.Services.PackageService.SendPackage(PackageId packageId)\r\n --- End of inner exception stack trace ---\r\n at Silanis.ESL.SDK.Services.PackageService.SendPackage(PackageId packageId)\r\n at Silanis.ESL.SDK.EslClient.SendPackage(PackageId id)\r\n" Adding more information, prior to this call, package is edited to update signers, after which immediately a document is added resulting in this exception. Thanks Uday