diff --git a/bagheeraview.py b/bagheeraview.py
index a1c9c80..3ed19fb 100755
--- a/bagheeraview.py
+++ b/bagheeraview.py
@@ -34,7 +34,7 @@ from itertools import groupby
 from PySide6.QtWidgets import (
     QApplication, QMainWindow, QWidget, QLabel, QVBoxLayout, QHBoxLayout, QLineEdit,
     QTextEdit, QPushButton, QFileDialog, QComboBox, QSlider, QMessageBox, QSizePolicy,
-    QMenu, QInputDialog, QTableWidget, QTableWidgetItem, QHeaderView, QTabWidget,
+    QMenu, QInputDialog, QTableWidget, QTableWidgetItem, QHeaderView, QTabWidget, QProgressDialog,
     QDockWidget, QAbstractItemView, QRadioButton, QButtonGroup, QListView,
     QStyledItemDelegate, QStyle, QDialog, QKeySequenceEdit, QDialogButtonBox
 )
@@ -2010,6 +2010,9 @@ class MainWindow(QMainWindow):
 
     def perform_shutdown(self):
         """Performs cleanup operations before the application closes."""
+        if getattr(self, '_is_shutting_down', False):
+            return
+        self._is_shutting_down = True
         self.is_cleaning = True
 
         # Save configuration early if visible, as per user request.
@@ -2017,6 +2020,24 @@ class MainWindow(QMainWindow):
         if self.isVisible():
             self.save_config()
 
+        # Stop all pending UI timers to prevent background tasks from triggering
+        self.hide_progress_timer.stop()
+        self.filter_input_timer.stop()
+        self.filter_refresh_timer.stop()
+        self.thumbnails_refresh_timer.stop()
+        self.rebuild_timer.stop()
+        self._model_update_timer.stop()
+        self.resume_scan_timer.stop()
+
+        # Close all viewers first to stop their preloader threads
+        self.close_all_viewers()
+
+        # Close duplicate manager if open to stop its preloader threads
+        if HAVE_IMAGEHASH:
+            for widget in QApplication.topLevelWidgets():
+                if isinstance(widget, DuplicateManagerDialog):
+                    widget.close()
+
         self.fs_watcher.stop()
         # 1. Stop all worker threads interacting with the cache
 
@@ -2053,7 +2074,19 @@ class MainWindow(QMainWindow):
 
         # Ensure all QRunnables in the shared thread pool are finished
         if self.thread_pool_manager:
-            self.thread_pool_manager.get_pool().waitForDone()
+            pool = self.thread_pool_manager.get_pool()
+            if pool.activeThreadCount() > 0:
+                progress = QProgressDialog(UITexts.SHUTTING_DOWN, None, 0, 0, self)
+                progress.setWindowTitle(PROG_NAME)
+                progress.setWindowModality(Qt.ApplicationModal)
+                progress.setMinimumDuration(0)
+                progress.show()
+
+                # Wait in small increments to keep the UI responsive
+                while not pool.waitForDone(100):
+                    if QApplication.instance():
+                        QApplication.processEvents()
+                progress.close()
 
         if self.duplicate_cache:
             self.duplicate_cache.lmdb_close()
diff --git a/duplicatecache.py b/duplicatecache.py
index 4655246..b4ace7b 100644
--- a/duplicatecache.py
+++ b/duplicatecache.py
@@ -571,6 +571,7 @@ class DuplicateDetector(QThread):
 
     def stop(self):
         self._is_running = False
+        self.wait() # Add this line
 
     def run(self):
         total_files = len(self.paths_to_scan)
diff --git a/duplicatedialog.py b/duplicatedialog.py
index 46e5f9e..6195c4f 100644
--- a/duplicatedialog.py
+++ b/duplicatedialog.py
@@ -143,6 +143,11 @@ class DuplicateManagerDialog(QDialog):
                 self.main_win.fs_watcher.file_moved.disconnect(self._on_file_moved_externally)
             except (RuntimeError, TypeError):
                 pass
+
+        if hasattr(self, 'left_pane') and self.left_pane:
+            self.left_pane.cleanup()
+        if hasattr(self, 'right_pane') and self.right_pane:
+            self.right_pane.cleanup()
         super().closeEvent(event)
 
     def resizeEvent(self, event):
diff --git a/imagecontroller.py b/imagecontroller.py
index 4cc5f21..034b225 100644
--- a/imagecontroller.py
+++ b/imagecontroller.py
@@ -42,6 +42,7 @@ class ImagePreloader(QThread):
     def __init__(self):
         """Initializes the preloader thread."""
         super().__init__()
+        self.setObjectName("ImagePreloaderThread")
         self.path = None
         self.index = -1
         self.mutex = QMutex()
diff --git a/imagescanner.py b/imagescanner.py
index e6db0a0..2e71463 100644
--- a/imagescanner.py
+++ b/imagescanner.py
@@ -134,13 +134,11 @@ class ScannerWorker(QRunnable):
         sizes_to_check = self.target_sizes if self.target_sizes is not None \
             else SCANNER_GENERATE_SIZES
 
-        if self._is_cancelled:
-            if self.semaphore:
-                self.semaphore.release()
-            return
-
-        fd = None
         try:
+            if self._is_cancelled:
+                return
+
+            fd = None
             # Optimize: Open file once to reuse FD for stat and xattrs
             fd = os.open(self.path, os.O_RDONLY)
             stat_res = os.fstat(fd)
@@ -285,6 +283,7 @@ class CacheWriter(QThread):
         self._condition_new_data = QWaitCondition()
         self._condition_space_available = QWaitCondition()
         # Soft limit for blocking producers (background threads)
+        self.setObjectName("CacheWriterThread") # Add this line
         self._max_size = 50
         self._running = True
 
@@ -334,6 +333,7 @@ class CacheWriter(QThread):
         self._running = False
         # Do not clear the queue here; let the run loop drain it to prevent data loss.
         self._condition_new_data.wakeAll()
+        logger.debug(f"{self.objectName()} stop requested, waking all.")
         self._condition_space_available.wakeAll()
         self._mutex.unlock()
 
@@ -380,6 +380,7 @@ class CacheWriter(QThread):
                     self.cache._batch_write_to_lmdb(batch)
                 except Exception as e:
                     logger.error(f"CacheWriter batch write error: {e}")
+        logger.debug(f"{self.objectName()} run method exiting.")
 
 
 class CacheLoader(QThread):
@@ -1328,6 +1329,7 @@ class CacheCleaner(QThread):
     def stop(self):
         """Signals the thread to stop."""
         self._is_running = False
+        self.wait()
 
     def run(self):
         self.setPriority(QThread.IdlePriority)
@@ -1914,3 +1916,4 @@ class ImageScanner(QThread):
         self.mutex.lock()
         self.condition.wakeAll()
         self.mutex.unlock()
+        self.wait()
diff --git a/settings.py b/settings.py
index 0347894..cc693ee 100644
--- a/settings.py
+++ b/settings.py
@@ -55,6 +55,7 @@ class DuplicateFileCounter(QThread):
 
     def stop(self):
         self._abort = True
+        self.wait() # Add this line
 
     def run(self):
         count = 0