Fixed: DownloadStation interface stuck in infinite loop in some cases.

* removed empty spaces. changed dcaex => ex

* Changed error message

* changed error message

* Wrong message, ups

* Another message

src/NzbDrone.Core/Download/Clients/DownloadStation/Proxies/DiskStationProxyBase.cs

@@ -49,7 +49,7 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation.Proxies
         {
             if (retries == 5)
             {
-                throw new DownloadClientException("Try to process same request more than 5 times");
+                throw new DownloadClientException("Try to process request to {0} with {1} more than 5 times", api, arguments.ToJson().ToString());
             }
 
             if (!_authenticated && api != DiskStationApi.Info && api != DiskStationApi.DSMInfo)
@@ -72,14 +72,20 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation.Proxies
                 }
                 else
                 {
+                    var msg = $"Failed to {operation}. Reason: {responseContent.Error.GetMessage(api)}";
+                    _logger.Error(msg);
+
                     if (responseContent.Error.SessionError)
                     {
                         _authenticated = false;
-                        return ProcessRequest<T>(api, arguments, settings, operation, method, retries++);
+
+                        if (responseContent.Error.Code == 105)
+                        {
+                            throw new DownloadClientAuthenticationException(msg);
                         }
 
-                    var msg = $"Failed to {operation}. Reason: {responseContent.Error.GetMessage(api)}";
-                    _logger.Error(msg);
+                        return ProcessRequest<T>(api, arguments, settings, operation, method, ++retries);
+                    }
                                      
                     throw new DownloadClientException(msg);
                 }

src/NzbDrone.Core/Download/Clients/DownloadStation/TorrentDownloadStation.cs

@@ -272,7 +272,17 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation
         {
             try
             {
-                var downloadDir = GetDownloadDirectory();
+                var downloadDir = GetDefaultDir();
+
+                if (downloadDir == null)
+                {
+                    return new NzbDroneValidationFailure(nameof(Settings.TvDirectory), "No default destination")
+                    {
+                        DetailedDescription = $"You must login into your Diskstation as {Settings.Username} and manually set it up into DownloadStation settings under BT/HTTP/FTP/NZB -> Location."
+                    };
+                }
+
+                downloadDir = GetDownloadDirectory();
 
                 if (downloadDir != null)
                 {
@@ -285,7 +295,7 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation
                     {
                         return new NzbDroneValidationFailure(fieldName, $"Shared folder does not exist")
                         {
-                            DetailedDescription = $"The DownloadStation does not have a Shared Folder with the name '{sharedFolder}', are you sure you specified it correctly?"
+                            DetailedDescription = $"The Diskstation does not have a Shared Folder with the name '{sharedFolder}', are you sure you specified it correctly?"
                         };
                     }
 
@@ -300,6 +310,11 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation
 
                 return null;
             }
+            catch (DownloadClientAuthenticationException ex) // User could not have permission to access to downloadstation
+            {
+                _logger.Error(ex);
+                return new NzbDroneValidationFailure(string.Empty, ex.Message);
+            }
             catch (Exception ex)
             {
                 _logger.Error(ex);

src/NzbDrone.Core/Download/Clients/DownloadStation/UsenetDownloadStation.cs

@@ -190,7 +190,17 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation
         {
             try
             {
-                var downloadDir = GetDownloadDirectory();
+                var downloadDir = GetDefaultDir();
+
+                if (downloadDir == null)
+                {
+                    return new NzbDroneValidationFailure(nameof(Settings.TvDirectory), "No default destination")
+                    {
+                        DetailedDescription = $"You must login into your Diskstation as {Settings.Username} and manually set it up into DownloadStation settings under BT/HTTP/FTP/NZB -> Location."
+                    };
+                }
+
+                downloadDir = GetDownloadDirectory();
 
                 if (downloadDir != null)
                 {
@@ -203,7 +213,7 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation
                     {
                         return new NzbDroneValidationFailure(fieldName, $"Shared folder does not exist")
                         {
-                            DetailedDescription = $"The DownloadStation does not have a Shared Folder with the name '{sharedFolder}', are you sure you specified it correctly?"
+                            DetailedDescription = $"The Diskstation does not have a Shared Folder with the name '{sharedFolder}', are you sure you specified it correctly?"
                         };
                     }
 
@@ -218,6 +228,11 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation
 
                 return null;
             }
+            catch (DownloadClientAuthenticationException ex) // User could not have permission to access to downloadstation
+            {
+                _logger.Error(ex);
+                return new NzbDroneValidationFailure(string.Empty, ex.Message);
+            }
             catch (Exception ex)
             {
                 _logger.Error(ex);