Do not call Resources.UnloadUnusedAssets() more than once every 3 mins

Assets/Scripts/Game/UserInterface/UserInterfaceWindow.cs

@@ -128,7 +128,7 @@ public void CloseWindow()
         {
             uiManager.PopWindow();
             RaiseOnCloseHandler();
-            Resources.UnloadUnusedAssets();
+            DaggerfallGC.ThrottledUnloadUnusedAssets();
         }
 
         public void PopWindow()

Assets/Scripts/Internal/DaggerfallGC.cs

@@ -0,0 +1,36 @@
+// Project:         Daggerfall Tools For Unity
+// Copyright:       Copyright (C) 2009-2020 Daggerfall Workshop
+// Web Site:        http://www.dfworkshop.net
+// License:         MIT License (http://www.opensource.org/licenses/mit-license.php)
+// Source Code:     https://github.com/Interkarma/daggerfall-unity
+// Original Author: Pango (petchema@concept-micro.com)
+// Contributors:    
+// 
+// Notes:
+//
+
+using System;
+using UnityEngine;
+
+namespace DaggerfallWorkshop
+{
+    public static class DaggerfallGC
+    {
+        // Min time between two unused assets collections
+        private const float uuaThrottleDelay = 180f;
+
+        private static float uuaTimer = Time.realtimeSinceStartup;
+
+        public static void ThrottledUnloadUnusedAssets()
+        {
+            if (Time.realtimeSinceStartup >= uuaTimer)
+                ForcedUnloadUnusedAssets();
+        }
+
+        public static void ForcedUnloadUnusedAssets()
+        {
+            Resources.UnloadUnusedAssets();
+            uuaTimer = Time.realtimeSinceStartup + uuaThrottleDelay;
+        }
+    }
+}

Assets/Scripts/Terrain/StreamingWorld.cs

@@ -659,7 +659,7 @@ private IEnumerator UpdateTerrains()
             if (init)
             {
                 DaggerfallUnity.Instance.MaterialReader.PruneCache();
-                Resources.UnloadUnusedAssets();
+                DaggerfallGC.ThrottledUnloadUnusedAssets();
             }
 
             // Set terrain neighbours