diff --git a/src/NzbDrone.Core.Test/Prowlarr.Core.Test.csproj b/src/NzbDrone.Core.Test/Prowlarr.Core.Test.csproj
index c792eca51..dbfd06861 100644
--- a/src/NzbDrone.Core.Test/Prowlarr.Core.Test.csproj
+++ b/src/NzbDrone.Core.Test/Prowlarr.Core.Test.csproj
@@ -6,7 +6,7 @@
     <PackageReference Include="Dapper" Version="2.0.123" />
     <PackageReference Include="NBuilder" Version="6.1.0" />
     <PackageReference Include="System.Data.SQLite.Core.Servarr" Version="1.0.115.5-18" />
-    <PackageReference Include="YamlDotNet" Version="15.1.2" />
+    <PackageReference Include="YamlDotNet" Version="13.1.1" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\NzbDrone.Test.Common\Prowlarr.Test.Common.csproj" />
diff --git a/src/NzbDrone.Core/IndexerVersions/IndexerDefinitionUpdateService.cs b/src/NzbDrone.Core/IndexerVersions/IndexerDefinitionUpdateService.cs
index 6b2c4dc91..4100934a0 100644
--- a/src/NzbDrone.Core/IndexerVersions/IndexerDefinitionUpdateService.cs
+++ b/src/NzbDrone.Core/IndexerVersions/IndexerDefinitionUpdateService.cs
@@ -137,11 +137,11 @@ namespace NzbDrone.Core.IndexerVersions
 
             if (directoryInfo.Exists)
             {
-                var files = directoryInfo.GetFiles($"*.yml", options);
+                var files = directoryInfo.GetFiles("*.yml", options);
 
                 foreach (var file in files)
                 {
-                    _logger.Debug("Loading definition " + file.FullName);
+                    _logger.Debug("Loading definition {0}", file.FullName);
 
                     try
                     {
@@ -158,9 +158,9 @@ namespace NzbDrone.Core.IndexerVersions
 
                         indexerList.Add(definition);
                     }
-                    catch (Exception e)
+                    catch (Exception ex)
                     {
-                        _logger.Error($"Error while parsing Cardigann definition {file.FullName}\n{e}");
+                        _logger.Error(ex, "Error while parsing Cardigann definition {0}", file.FullName);
                     }
                 }
             }
@@ -188,7 +188,8 @@ namespace NzbDrone.Core.IndexerVersions
                 if (files.Any())
                 {
                     var file = files.First();
-                    _logger.Trace("Loading Cardigann definition " + file.FullName);
+                    _logger.Trace("Loading Cardigann definition {0}", file.FullName);
+
                     try
                     {
                         var definitionString = File.ReadAllText(file.FullName);
@@ -196,9 +197,9 @@ namespace NzbDrone.Core.IndexerVersions
 
                         return CleanIndexerDefinition(definition);
                     }
-                    catch (Exception e)
+                    catch (Exception ex)
                     {
-                        _logger.Error($"Error while parsing Cardigann definition {file.FullName}\n{e}");
+                        _logger.Error(ex, "Error while parsing Cardigann definition {0}", file.FullName);
                     }
                 }
             }
@@ -206,7 +207,7 @@ namespace NzbDrone.Core.IndexerVersions
             var dbDefs = _versionService.All();
 
             //Check to ensure it's in versioned defs before we go to web
-            if (dbDefs.Count > 0 && !dbDefs.Any(x => x.File == fileKey))
+            if (dbDefs.Count > 0 && dbDefs.All(x => x.File != fileKey))
             {
                 throw new ArgumentNullException(nameof(fileKey));
             }
@@ -217,9 +218,10 @@ namespace NzbDrone.Core.IndexerVersions
 
         private CardigannDefinition GetHttpDefinition(string id)
         {
-            var req = new HttpRequest($"https://indexers.prowlarr.com/{DEFINITION_BRANCH}/{DEFINITION_VERSION}/{id}");
-            var response = _httpClient.Get(req);
+            var request = new HttpRequest($"https://indexers.prowlarr.com/{DEFINITION_BRANCH}/{DEFINITION_VERSION}/{id}");
+            var response = _httpClient.Get(request);
             var definition = _deserializer.Deserialize<CardigannDefinition>(response.Content);
+
             return CleanIndexerDefinition(definition);
         }
 
@@ -289,7 +291,7 @@ namespace NzbDrone.Core.IndexerVersions
                 EnsureDefinitionsFolder();
 
                 var definitionsFolder = Path.Combine(startupFolder, "Definitions");
-                var saveFile = Path.Combine(definitionsFolder, $"indexers.zip");
+                var saveFile = Path.Combine(definitionsFolder, "indexers.zip");
 
                 _httpClient.DownloadFile($"https://indexers.prowlarr.com/{DEFINITION_BRANCH}/{DEFINITION_VERSION}/package.zip", saveFile);
 
diff --git a/src/NzbDrone.Core/Indexers/IndexerFactory.cs b/src/NzbDrone.Core/Indexers/IndexerFactory.cs
index 53c2c2838..a5f4e6601 100644
--- a/src/NzbDrone.Core/Indexers/IndexerFactory.cs
+++ b/src/NzbDrone.Core/Indexers/IndexerFactory.cs
@@ -55,10 +55,10 @@ namespace NzbDrone.Core.Indexers
                     {
                         MapCardigannDefinition(definition);
                     }
-                    catch
+                    catch (Exception ex)
                     {
                         // Skip indexer if we fail in Cardigann mapping
-                        _logger.Debug("Indexer '{0}' has no definition", definition.Name);
+                        _logger.Debug(ex, "Indexer '{0}' has no definition", definition.Name);
                     }
                 }
 
diff --git a/src/NzbDrone.Core/Prowlarr.Core.csproj b/src/NzbDrone.Core/Prowlarr.Core.csproj
index 4645bc246..b9ab1d826 100644
--- a/src/NzbDrone.Core/Prowlarr.Core.csproj
+++ b/src/NzbDrone.Core/Prowlarr.Core.csproj
@@ -21,7 +21,7 @@
     <PackageReference Include="System.Data.SQLite.Core.Servarr" Version="1.0.115.5-18" />
     <PackageReference Include="System.Text.Json" Version="6.0.9" />
     <PackageReference Include="MonoTorrent" Version="2.0.7" />
-    <PackageReference Include="YamlDotNet" Version="15.1.2" />
+    <PackageReference Include="YamlDotNet" Version="13.1.1" />
     <PackageReference Include="AngleSharp" Version="1.1.2" />
   </ItemGroup>
   <ItemGroup>