diff --git a/Emby.Server.Implementations/HttpClientManager/HttpClientManager.cs b/Emby.Server.Implementations/HttpClientManager/HttpClientManager.cs
index 0dd4d4ca5b..0e6083773d 100644
--- a/Emby.Server.Implementations/HttpClientManager/HttpClientManager.cs
+++ b/Emby.Server.Implementations/HttpClientManager/HttpClientManager.cs
@@ -83,7 +83,16 @@ namespace Emby.Server.Implementations.HttpClientManager
 
             var request = new HttpRequestMessage(method, url);
 
-            AddRequestHeaders(request, options);
+            foreach (var header in options.RequestHeaders)
+            {
+                request.Headers.TryAddWithoutValidation(header.Key, header.Value);
+            }
+
+            if (options.EnableDefaultUserAgent
+                && !request.Headers.TryGetValues(HeaderNames.UserAgent, out _))
+            {
+                request.Headers.Add(HeaderNames.UserAgent, _defaultUserAgentFn());
+            }
 
             switch (options.DecompressionMethod)
             {
@@ -121,26 +130,6 @@ namespace Emby.Server.Implementations.HttpClientManager
             return request;
         }
 
-        private void AddRequestHeaders(HttpRequestMessage request, HttpRequestOptions options)
-        {
-            var hasUserAgent = false;
-
-            foreach (var header in options.RequestHeaders)
-            {
-                if (string.Equals(header.Key, HeaderNames.UserAgent, StringComparison.OrdinalIgnoreCase))
-                {
-                    hasUserAgent = true;
-                }
-
-                request.Headers.Add(header.Key, header.Value);
-            }
-
-            if (!hasUserAgent && options.EnableDefaultUserAgent)
-            {
-                request.Headers.Add(HeaderNames.UserAgent, _defaultUserAgentFn());
-            }
-        }
-
         /// <summary>
         /// Gets the response internal.
         /// </summary>
diff --git a/MediaBrowser.Api/Playback/BaseStreamingService.cs b/MediaBrowser.Api/Playback/BaseStreamingService.cs
index 17aa6b23a6..8c4ccfa22c 100644
--- a/MediaBrowser.Api/Playback/BaseStreamingService.cs
+++ b/MediaBrowser.Api/Playback/BaseStreamingService.cs
@@ -956,7 +956,10 @@ namespace MediaBrowser.Api.Playback
                 if (string.Equals(GetHeader("getMediaInfo.sec"), "1", StringComparison.OrdinalIgnoreCase))
                 {
                     var ms = TimeSpan.FromTicks(state.RunTimeTicks.Value).TotalMilliseconds;
-                    responseHeaders["MediaInfo.sec"] = string.Format("SEC_Duration={0};", Convert.ToInt32(ms).ToString(CultureInfo.InvariantCulture));
+                    responseHeaders["MediaInfo.sec"] = string.Format(
+                        CultureInfo.InvariantCulture,
+                        "SEC_Duration={0};",
+                        Convert.ToInt32(ms));
                 }
 
                 if (!isStaticallyStreamed && profile != null)
@@ -974,8 +977,7 @@ namespace MediaBrowser.Api.Playback
 
             if (state.VideoRequest == null)
             {
-                responseHeaders["contentFeatures.dlna.org"] = new ContentFeatureBuilder(profile)
-                    .BuildAudioHeader(
+                responseHeaders["contentFeatures.dlna.org"] = new ContentFeatureBuilder(profile).BuildAudioHeader(
                     state.OutputContainer,
                     audioCodec,
                     state.OutputAudioBitrate,
@@ -984,15 +986,13 @@ namespace MediaBrowser.Api.Playback
                     state.OutputAudioBitDepth,
                     isStaticallyStreamed,
                     state.RunTimeTicks,
-                    state.TranscodeSeekInfo
-                    );
+                    state.TranscodeSeekInfo);
             }
             else
             {
                 var videoCodec = state.ActualOutputVideoCodec;
 
-                responseHeaders["contentFeatures.dlna.org"] = new ContentFeatureBuilder(profile)
-                    .BuildVideoHeader(
+                responseHeaders["contentFeatures.dlna.org"] = new ContentFeatureBuilder(profile).BuildVideoHeader(
                     state.OutputContainer,
                     videoCodec,
                     audioCodec,
@@ -1014,9 +1014,7 @@ namespace MediaBrowser.Api.Playback
                     state.TargetVideoStreamCount,
                     state.TargetAudioStreamCount,
                     state.TargetVideoCodecTag,
-                    state.IsTargetAVC
-
-                    ).FirstOrDefault() ?? string.Empty;
+                    state.IsTargetAVC).FirstOrDefault() ?? string.Empty;
             }
         }
 
@@ -1025,8 +1023,16 @@ namespace MediaBrowser.Api.Playback
             var runtimeSeconds = TimeSpan.FromTicks(state.RunTimeTicks.Value).TotalSeconds.ToString(CultureInfo.InvariantCulture);
             var startSeconds = TimeSpan.FromTicks(state.Request.StartTimeTicks ?? 0).TotalSeconds.ToString(CultureInfo.InvariantCulture);
 
-            responseHeaders["TimeSeekRange.dlna.org"] = string.Format("npt={0}-{1}/{1}", startSeconds, runtimeSeconds);
-            responseHeaders["X-AvailableSeekRange"] = string.Format("1 npt={0}-{1}", startSeconds, runtimeSeconds);
+            responseHeaders["TimeSeekRange.dlna.org"] = string.Format(
+                CultureInfo.InvariantCulture,
+                "npt={0}-{1}/{1}",
+                startSeconds,
+                runtimeSeconds);
+            responseHeaders["X-AvailableSeekRange"] = string.Format(
+                CultureInfo.InvariantCulture,
+                "1 npt={0}-{1}",
+                startSeconds,
+                runtimeSeconds);
         }
     }
 }
diff --git a/MediaBrowser.Api/Playback/Progressive/BaseProgressiveStreamingService.cs b/MediaBrowser.Api/Playback/Progressive/BaseProgressiveStreamingService.cs
index c15681654b..97c1a7a496 100644
--- a/MediaBrowser.Api/Playback/Progressive/BaseProgressiveStreamingService.cs
+++ b/MediaBrowser.Api/Playback/Progressive/BaseProgressiveStreamingService.cs
@@ -280,18 +280,24 @@ namespace MediaBrowser.Api.Playback.Progressive
         /// <param name="isHeadRequest">if set to <c>true</c> [is head request].</param>
         /// <param name="cancellationTokenSource">The cancellation token source.</param>
         /// <returns>Task{System.Object}.</returns>
-        private async Task<object> GetStaticRemoteStreamResult(StreamState state, Dictionary<string, string> responseHeaders, bool isHeadRequest, CancellationTokenSource cancellationTokenSource)
+        private async Task<object> GetStaticRemoteStreamResult(
+            StreamState state,
+            Dictionary<string, string> responseHeaders,
+            bool isHeadRequest,
+            CancellationTokenSource cancellationTokenSource)
         {
-            state.RemoteHttpHeaders.TryGetValue(HeaderNames.UserAgent, out var useragent);
-
             var options = new HttpRequestOptions
             {
                 Url = state.MediaPath,
-                UserAgent = useragent,
                 BufferContent = false,
                 CancellationToken = cancellationTokenSource.Token
             };
 
+            if (state.RemoteHttpHeaders.TryGetValue(HeaderNames.UserAgent, out var useragent))
+            {
+                options.UserAgent = useragent;
+            }
+
             var response = await HttpClient.GetResponse(options).ConfigureAwait(false);
 
             responseHeaders[HeaderNames.AcceptRanges] = "none";
@@ -306,7 +312,7 @@ namespace MediaBrowser.Api.Playback.Progressive
             {
                 using (response)
                 {
-                    return ResultFactory.GetResult(null, new byte[] { }, response.ContentType, responseHeaders);
+                    return ResultFactory.GetResult(null, Array.Empty<byte>(), response.ContentType, responseHeaders);
                 }
             }
 
diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index 963091673e..841205d0ce 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -168,9 +168,7 @@ namespace MediaBrowser.Controller.MediaEncoding
         /// <returns>System.String.</returns>
         public string GetUserAgentParam(EncodingJobInfo state)
         {
-            state.RemoteHttpHeaders.TryGetValue("User-Agent", out string useragent);
-
-            if (!string.IsNullOrEmpty(useragent))
+            if (state.RemoteHttpHeaders.TryGetValue("User-Agent", out string useragent))
             {
                 return "-user_agent \"" + useragent + "\"";
             }
diff --git a/MediaBrowser.Model/Dlna/ContentFeatureBuilder.cs b/MediaBrowser.Model/Dlna/ContentFeatureBuilder.cs
index e52951dd08..2333fa7a02 100644
--- a/MediaBrowser.Model/Dlna/ContentFeatureBuilder.cs
+++ b/MediaBrowser.Model/Dlna/ContentFeatureBuilder.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using MediaBrowser.Model.MediaInfo;
 
 namespace MediaBrowser.Model.Dlna
@@ -81,17 +82,20 @@ namespace MediaBrowser.Model.Dlna
             //    flagValue = flagValue | DlnaFlags.TimeBasedSeek;
             //}
 
-            string dlnaflags = string.Format(";DLNA.ORG_FLAGS={0}",
-             DlnaMaps.FlagsToString(flagValue));
+            string dlnaflags = string.Format(
+                CultureInfo.InvariantCulture,
+                ";DLNA.ORG_FLAGS={0}",
+                DlnaMaps.FlagsToString(flagValue));
 
-            ResponseProfile mediaProfile = _profile.GetAudioMediaProfile(container,
+            ResponseProfile mediaProfile = _profile.GetAudioMediaProfile(
+                container,
                 audioCodec,
                 audioChannels,
                 audioBitrate,
                 audioSampleRate,
                 audioBitDepth);
 
-            string orgPn = mediaProfile == null ? null : mediaProfile.OrgPn;
+            string orgPn = mediaProfile?.OrgPn;
 
             if (string.IsNullOrEmpty(orgPn))
             {