I am working on an app that talks with Dynamics CRM Online 2016.

I am patching a simple object to contacts. Payload looks something like this -

PATCH https://.crm4.dynamics.com/api/data/v8.1/contacts(00000000-0000-0000-0000-000000000000)
{
  "emailaddress1": "test@emailaddress.com",
  "firstname": "John"
}

This works in Postman or any other REST client. However if I do it from app which is patching approx 34 contacts in parallel (4 at a time). I am getting this exception for most of the contacts -

{
  "error":{
    "code":"","message":"Generic SQL error.","innererror":{
      "message":"Generic SQL error.","type":"System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]","stacktrace":"   at Microsoft.Crm.Extensibility.OrganizationSdkServiceInternal.Execute(OrganizationRequest request, CorrelationToken correlationToken, CallerOriginToken callerOriginToken, WebServiceType serviceType, Boolean checkAdminMode, ExecutionContext executionContext)\r\n   at Microsoft.Crm.Extensibility.OData.CrmODataExecutionContext.Upsert(Entity entity)\r\n   at Microsoft.Crm.Extensibility.OData.CrmODataExecutionContext.Update(Entity entity, UpdateOption updateOption)\r\n   at Microsoft.Crm.Extensibility.OData.CrmODataServiceDataProvider.UpdateEdmEntity(CrmODataExecutionContext context, String edmEntityName, String entityKeyValue, EdmEntityObject entityObject)\r\n   at Microsoft.Crm.Extensibility.OData.EntityController.PatchEntity(String entityName, String key, EdmEntityObject entityDelta)\r\n   at lambda_method(Closure , Object , Object[] )\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.b__9(Object instance, Object[] methodParameters)\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at System.Web.Http.Controllers.ApiControllerActionInvoker.d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at System.Web.Http.Controllers.ActionFilterResult.d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at System.Web.Http.Dispatcher.HttpControllerDispatcher.d__1.MoveNext()"
    }
  }
}

I tried searching for possible solutions on internet but couldn't find any.