Application Insights .net core : Process was called on the TelemetrySink after it was disposed, the telemetry data was dropped

We have noticed several situations where telemetry has not showed up in AI. After some digging I found entries like this in the log from FileDiagnosticsTelemetryModule.

Microsoft.ApplicationInsights.Extensibility.TraceSource Error: 43 : Process was called on the TelemetrySink after it was disposed, the telemetry data was dropped.

Sometimes telemetry arrives, sometimes not. There is only one other post I found on this but the article did not address much. Has anyone seen this before? Anything I should be looking at?

Startup.cs

ConfigureXXXServices

   ` services.AddSingleton<ITelemetryInitializer>(new RoleNameInitializer(ApplicationName));  
    services.AddSingleton(new OperationCorrelationTelemetryInitializer());
    services.AddSingleton(new HttpDependenciesParsingTelemetryInitializer());

    var aiOptions = new Microsoft.ApplicationInsights.AspNetCore.Extensions.ApplicationInsightsServiceOptions
    {
        EnableAdaptiveSampling                    = false,
        DeveloperMode                             = false,
        EnableDebugLogger                         = true,
        EnableQuickPulseMetricStream              = true,
        ApplicationVersion                        = "2.0.0",
        EnableDependencyTrackingTelemetryModule   = true,
        EnableRequestTrackingTelemetryModule      = true,
        AddAutoCollectedMetricExtractor           = true,
        EnableAppServicesHeartbeatTelemetryModule = true,
        EnableEventCounterCollectionModule        = true,
        //EnablePerformanceCounterCollectionModule = true,                
        InstrumentationKey                         = Configuration.GetSection("Logging")["LoggingServiceApiKey"],                   
    };

    services.AddSingleton(typeof(ITelemetryChannel), new ServerTelemetryChannel() { StorageFolder = @"c:\TelemetryService_ReportingAgent" });
    services.AddApplicationInsightsTelemetry(aiOptions);
    services.AddApplicationInsightsTelemetryProcessor<CustomTraceOnlyProcessor>();
    services.AddScoped<LogContext>();
    services.AddSingleton<ITelemetryInitializer, LogContextInitializer>();          

    //if (Environment == "Local")
    //{
    Console.WriteLine("Setting up Telemetry Channel Diagnostics Tracing. See c:\\logs for details..");
    services.AddSingleton<ITelemetryModule, Microsoft.ApplicationInsights.Extensibility.Implementation.Tracing.FileDiagnosticsTelemetryModule>();

    services.ConfigureTelemetryModule<Microsoft.ApplicationInsights.Extensibility.Implementation.Tracing.FileDiagnosticsTelemetryModule>((module, options) =>
    {
        module.LogFilePath = "C:\\logs";
        module.LogFileName = ApplicationName + "_TelemetryChannelLog.txt";
        module.Severity    = "Verbose";
    });
    //}


    services.AddLogging(builder =>
    {
        builder.AddApplicationInsights(Configuration.GetSection("Logging")["LoggingServiceApiKey"]);
        builder.AddFilter<ApplicationInsightsLoggerProvider>("", LogLevel.Information);
        builder.AddFilter<ApplicationInsightsLoggerProvider>("Microsoft", LogLevel.Error);
    });`

ConfigureXXX

   `   // Could these be the Telemetry Sinks getting disposed of too soon?

      loggerFactory.AddDebug(LogLevel.Debug);
      loggerFactory.AddConsole(Configuration.GetSection("Logging"));   

      appLifetime.ApplicationStopping.Register(OnShutdown);

      private void OnShutdown()
      {
       Console.WriteLine("Shutting Down");
       this.TelemetryClient.Flush();   // this.TelemetryClient is a non-DI supplied instance (new) created in ctor..
       Thread.Sleep(9000);             // was 5000. 
      }`

Thanks for your time looking over this. Any help is appreciated.. Travis