diff --git a/electrum/gui/qt/__init__.py b/electrum/gui/qt/__init__.py
index 61c80c9fb..cdfe9d538 100644
--- a/electrum/gui/qt/__init__.py
+++ b/electrum/gui/qt/__init__.py
@@ -329,7 +329,7 @@ class ElectrumGui(Logger):
 
     def close_window(self, window: ElectrumWindow):
         if window in self.windows:
-           self.windows.remove(window)
+            self.windows.remove(window)
         self.build_tray_menu()
         # save wallet path of last open window
         if not self.windows:
@@ -375,6 +375,9 @@ class ElectrumGui(Logger):
         self.app.lastWindowClosed.connect(quit_after_last_window)
 
         def clean_up():
+            # If there are still some open windows, try to clean them up.
+            for window in list(self.windows):
+                window.clean_up()
             # Shut down the timer cleanly
             self.timer.stop()
             # clipboard persistence. see http://www.mail-archive.com/pyqt@riverbankcomputing.com/msg17328.html
diff --git a/electrum/gui/qt/main_window.py b/electrum/gui/qt/main_window.py
index 3e9d75eb4..acae82c38 100644
--- a/electrum/gui/qt/main_window.py
+++ b/electrum/gui/qt/main_window.py
@@ -190,7 +190,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         self.contacts = wallet.contacts
         self.tray = gui_object.tray
         self.app = gui_object.app
-        self.cleaned_up = False
+        self._cleaned_up = False
         self.payment_request = None  # type: Optional[paymentrequest.PaymentRequest]
         self.payto_URI = None
         self.checking_accounts = False
@@ -300,6 +300,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
                                        _("Would you like to be notified when there is a newer version of Electrum available?"))
             config.set_key('check_updates', bool(choice), save=True)
 
+        self._update_check_thread = None
         if config.get('check_updates', False):
             # The references to both the thread and the window need to be stored somewhere
             # to prevent GC from getting in our way.
@@ -496,7 +497,6 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
     def close_wallet(self):
         if self.wallet:
             self.logger.info(f'close_wallet {self.wallet.storage.path}')
-            self.wallet.thread = None
         run_hook('close_wallet', self.wallet)
 
     @profiler
@@ -3158,14 +3158,17 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
             self.show_warning(_('Please restart Electrum to activate the new GUI settings'), title=_('Success'))
 
     def closeEvent(self, event):
-        # It seems in some rare cases this closeEvent() is called twice
-        if not self.cleaned_up:
-            self.cleaned_up = True
-            self.clean_up()
+        # note that closeEvent is NOT called if the user quits with Ctrl-C
+        self.clean_up()
         event.accept()
 
     def clean_up(self):
-        self.wallet.thread.stop()
+        if self._cleaned_up:
+            return
+        self._cleaned_up = True
+        if self.wallet.thread:
+            self.wallet.thread.stop()
+            self.wallet.thread = None
         util.unregister_callback(self.on_network)
         self.config.set_key("is_maximized", self.isMaximized())
         if not self.isMaximized():
@@ -3177,6 +3180,9 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
             self.qr_window.close()
         self.close_wallet()
 
+        if self._update_check_thread:
+            self._update_check_thread.exit()
+            self._update_check_thread.wait()
         self.gui_object.timer.timeout.disconnect(self.timer_actions)
         self.gui_object.close_window(self)
 
diff --git a/electrum/gui/qt/network_dialog.py b/electrum/gui/qt/network_dialog.py
index cce54683c..5085e246b 100644
--- a/electrum/gui/qt/network_dialog.py
+++ b/electrum/gui/qt/network_dialog.py
@@ -65,6 +65,7 @@ class NetworkDialog(QDialog):
         self.network_updated_signal_obj.network_updated_signal.connect(
             self.on_update)
         util.register_callback(self.on_network, ['network_updated'])
+        self._cleaned_up = False
 
     def on_network(self, event, *args):
         self.network_updated_signal_obj.network_updated_signal.emit(event, args)
@@ -72,6 +73,14 @@ class NetworkDialog(QDialog):
     def on_update(self):
         self.nlayout.update()
 
+    def closeEvent(self, event):
+        if not self._cleaned_up:
+            self._cleaned_up = True
+            self.clean_up()
+        event.accept()
+
+    def clean_up(self):
+        self.nlayout.clean_up()
 
 
 class NodesListWidget(QTreeWidget):
@@ -308,6 +317,13 @@ class NetworkChoiceLayout(object):
         self.fill_in_proxy_settings()
         self.update()
 
+    def clean_up(self):
+        if self.td:
+            self.td.found_proxy.disconnect()
+            self.td.exit()
+            self.td.wait()
+            self.td = None
+
     def check_disable_proxy(self, b):
         if not self.config.is_modifiable('proxy'):
             b = False
diff --git a/electrum/gui/qt/util.py b/electrum/gui/qt/util.py
index 6330ab1d0..473865b46 100644
--- a/electrum/gui/qt/util.py
+++ b/electrum/gui/qt/util.py
@@ -914,6 +914,8 @@ class TaskThread(QThread):
 
     def stop(self):
         self.tasks.put(None)
+        self.exit()
+        self.wait()
 
 
 class ColorSchemeItem: