diff --git a/API/RenderSession.cs b/API/RenderSession.cs
index 680c508..56ad5da 100644
--- a/API/RenderSession.cs
+++ b/API/RenderSession.cs
@@ -520,7 +520,9 @@ public class RenderSession
         }
         
         RenderManager.Instance.levelPath = levelPath;
-        RenderManager.Instance.Configuration = renderConfig;
+        // The render uses its own copy of the configuration: values adjusted during the render
+        // (e.g. the audio sample rate in SetupPlay) stay in this copy and do not change the caller's object.
+        RenderManager.Instance.Configuration = renderConfig.Clone();
 
         RenderManager.Instance.stage = RenderStage.Load;
         
diff --git a/UI/Window/RenderConfigWindow.cs b/UI/Window/RenderConfigWindow.cs
index 34c4950..147da04 100644
--- a/UI/Window/RenderConfigWindow.cs
+++ b/UI/Window/RenderConfigWindow.cs
@@ -9,6 +9,7 @@ using ADOFAIRenderer.Data;
 using ADOFAIRenderer.Localization;
 using ADOFAIRenderer.Util.OS;
 using MelonLoader;
+using Newtonsoft.Json;
 using O5Kit.Control;
 using O5Kit.Core;
 using O5Kit.Factory;
@@ -32,6 +33,14 @@ internal static class RenderConfigWindow
     private static Coroutine? _deleteResetCoroutine;
     private static string? _lastLoadedPresetName;
 
+    /// <summary>
+    /// Configuration edited by this window. Kept for the whole game session; a render started from the window
+    /// receives a copy of it (RenderSession.Start), so values adjusted during the render are not written back here.
+    /// </summary>
+    private static RenderConfig? _uiConfig;
+
+    private static RenderConfig UiConfig => _uiConfig ??= new RenderConfig();
+
     // Controls cache for validation & sync
     private static O5Slider? _renderFpsSlider;
     private static O5Slider? _videoFPSSlider;
@@ -111,8 +120,7 @@ internal static class RenderConfigWindow
             ReloadPresetDropdown(GlobalSettings.Current.LastPresetName);
         }
         
-        // ReSharper disable once NullCoalescingConditionIsAlwaysNotNullAccordingToAPIContract
-        var config = RenderManager.Instance.Configuration ??= new RenderConfig();
+        var config = UiConfig;
         ApplyConfigToUI(config);
 
         SetWindowActive(true);
@@ -125,8 +133,7 @@ internal static class RenderConfigWindow
         var (_, scrollContent, _) =
             O5Factory.ScrollView(ctx, content, spacing: 10f, padding: 8f);
 
-        // ReSharper disable once NullCoalescingConditionIsAlwaysNotNullAccordingToAPIContract
-        var config = RenderManager.Instance.Configuration ??= new RenderConfig();
+        var config = UiConfig;
         EnsureDefaultConfig(config);
 
         double[] renderFpsSnap = { 23.976, 24, 29.97, 30, 59.94, 60, 144, 
@@ -744,11 +751,14 @@ internal static class RenderConfigWindow
     {
         EnsureDefaultConfig(config);
 
-        _renderFpsSlider?.Set((float) config.RenderFPS, false);
-        _videoFPSSlider?.Set((float) config.VideoFPS, false);
-        _renderWidthSlider?.Set(config.RenderWidth, false);
-        _renderHeightSlider?.Set(config.RenderHeight, false);
-        _delayAfterEndSlider?.Set((float) config.DelayAfterEnd, false);
+        // Sliders show the config values as they are (noFilter: true).
+        // O5Slider.Set applies the slider filter (snapping to the nearest snap value) unless noFilter is set;
+        // the filter is meant for dragging, and typed values are not snapped either (O5Slider.SetFromInput).
+        _renderFpsSlider?.Set(config.RenderFPS, false, noFilter: true);
+        _videoFPSSlider?.Set(config.VideoFPS, false, noFilter: true);
+        _renderWidthSlider?.Set(config.RenderWidth, false, noFilter: true);
+        _renderHeightSlider?.Set(config.RenderHeight, false, noFilter: true);
+        _delayAfterEndSlider?.Set(config.DelayAfterEnd, false, noFilter: true);
         _showJudgementToggle?.Set(config.ShowJudgementText, false);
 
         _codecDropdown?.Set(config.VideoConfig.Codec, false);
@@ -756,13 +766,13 @@ internal static class RenderConfigWindow
         _bitrateInput?.Set(config.VideoConfig.Bitrate.ToString(), false);
         _maxBitrateInput?.Set(config.VideoConfig.MaxBitrate.ToString(), false);
         _qpInput?.Set(config.VideoConfig.QP.ToString(), false);
-        _keyframeIntervalSlider?.Set(config.VideoConfig.KeyframeInterval, false);
+        _keyframeIntervalSlider?.Set(config.VideoConfig.KeyframeInterval, false, noFilter: true);
         _forceSoftwareToggle?.Set(config.VideoConfig.ForceSoftwareEncoder, false);
 
         _renderAudioToggle?.Set(config.AudioConfig.RenderAudio, false);
         _sampleRateDropdown?.Set(config.AudioConfig.AudioSampleRate, false);
         _channelsDropdown?.Set(config.AudioConfig.AudioChannels, false);
-        _audioBitrateSlider?.Set(config.AudioConfig.AudioBitrate / 1000.0, false);
+        _audioBitrateSlider?.Set(config.AudioConfig.AudioBitrate / 1000.0, false, noFilter: true);
 
         _outputDirInput?.Set(GlobalSettings.EffectiveOutputDirectory, false);
 
@@ -789,17 +799,51 @@ internal static class RenderConfigWindow
         UpdateVideoCodecUI(config.VideoConfig.Codec, config);
         UpdateRateControlUI(config.VideoConfig.RateControlMode, noAnimate: true);
 
-        if (!string.IsNullOrEmpty(GlobalSettings.Current.LastPresetName))
+        UpdatePresetLabel(config);
+    }
+
+    /// <summary>
+    /// Sets the preset dropdown from the config values.
+    ///   Every value equals the last loaded preset (_lastLoadedPresetName): the preset name is shown.
+    ///   Any value differs (edited, or the preset file changed): the Custom label is shown (MarkConfigModified),
+    ///   the same state as after editing a value in the window.
+    /// </summary>
+    private static void UpdatePresetLabel(RenderConfig config)
+    {
+        if (_presetDropdown == null) return;
+
+        var presetName = _lastLoadedPresetName;
+        var preset = string.IsNullOrEmpty(presetName)
+            ? null
+            : PresetManager.GetPresets().FirstOrDefault(p => string.Equals(p.Name, presetName, StringComparison.OrdinalIgnoreCase));
+
+        if (preset == null || !ConfigValuesEqual(config, preset.Config))
         {
-            _presetDropdown?.Set(GlobalSettings.Current.LastPresetName, false);
-            _lastLoadedPresetName = GlobalSettings.Current.LastPresetName;
-            UpdateDeleteButtonState();
+            MarkConfigModified();
+            return;
         }
+
+        if (_presetDropdown.Values.Contains(CustomPresetLabel))
+        {
+            _presetDropdown.SetValues(_presetDropdown.Values.Where(v => v != CustomPresetLabel).ToList());
+        }
+        _presetDropdown.Set(preset.Name, false);
+        UpdateDeleteButtonState();
+    }
+
+    /// <summary>
+    /// Compares two configs by their serialized JSON (the same form as the preset files), so every saved value is compared.
+    /// </summary>
+    private static bool ConfigValuesEqual(RenderConfig a, RenderConfig b)
+    {
+        var settings = new JsonSerializerSettings();
+        settings.Converters.Add(new ColorJsonConverter());
+        return JsonConvert.SerializeObject(a, settings) == JsonConvert.SerializeObject(b, settings);
     }
 
     private static void TryGoRender()
     {
-        var config = RenderManager.Instance.Configuration;
+        var config = UiConfig;
         SyncUItoConfig(config);
 
         // Sync Output Directory