Force min 4 threads in pool

src/NzbDrone.Host/ApplicationServer.cs

@@ -1,4 +1,6 @@
+using System;
 using System.ServiceProcess;
+using System.Threading;
 using NLog;
 using NzbDrone.Common.Composition;
 using NzbDrone.Common.EnvironmentInfo;
@@ -89,6 +91,9 @@ namespace Radarr.Host
                 //_cancelHandler = new CancelHandler();
             }
 
+            ThreadPool.GetMinThreads(out var minWorker, out var minIOC);
+            ThreadPool.SetMinThreads(Math.Max(4, minWorker), Math.Max(4, minIOC));
+
             _runtimeInfo.IsExiting = false;
             DbFactory.RegisterDatabase(_container);
             _hostController.StartServer();