diff --git a/Furious/Widget/UserServersQTableWidget.py b/Furious/Widget/UserServersQTableWidget.py
index 5e95510..b5653ef 100644
--- a/Furious/Widget/UserServersQTableWidget.py
+++ b/Furious/Widget/UserServersQTableWidget.py
@@ -45,6 +45,7 @@
 import logging
 import icmplib
 import functools
+import threading
 
 __all__ = ['UserServersQTableWidget']
 
@@ -811,6 +812,9 @@ def __init__(self, *args, **kwargs):
 
         # Distinguish double-click and activated
         self.doubleClickedFlag = False
+
+        self.guiEditorMutex = threading.Lock()
+
         # Signals
         self.itemChanged.connect(self.handleItemChanged)
         self.itemSelectionChanged.connect(self.handleItemSelectionChanged)
@@ -914,38 +918,39 @@ def getGuiEditorByFactory(self, factory, **kwargs):
 
     @QtCore.Slot(QTableWidgetItem)
     def handleItemDoubleClicked(self, item: QTableWidgetItem):
-        self.doubleClickedFlag = True
+        with self.guiEditorMutex:
+            self.doubleClickedFlag = True
 
-        index = item.row()
-        factory = AS_UserServers()[index]
+            index = item.row()
+            factory = AS_UserServers()[index]
 
-        guiEditor = self.getGuiEditorByFactory(factory, translatable=False)
+            guiEditor = self.getGuiEditorByFactory(factory, translatable=False)
 
-        if guiEditor is None:
-            # Unrecognized. Do nothing
-            return
+            if guiEditor is None:
+                # Unrecognized. Do nothing
+                return
 
-        # Dummy ref
-        setattr(self, '_guiEditorRef0', guiEditor)
+            # Dummy ref
+            setattr(self, '_guiEditorRef0', guiEditor)
 
-        guiEditor.setWindowTitle(f'{index + 1} - ' + factory.getExtras('remark'))
+            guiEditor.setWindowTitle(f'{index + 1} - ' + factory.getExtras('remark'))
 
-        try:
-            guiEditor.factoryToInput(factory)
-        except Exception as ex:
-            # Any non-exit exceptions
+            try:
+                guiEditor.factoryToInput(factory)
+            except Exception as ex:
+                # Any non-exit exceptions
 
-            logger.error(f'error while converting factory to input: {ex}')
+                logger.error(f'error while converting factory to input: {ex}')
 
-        guiEditor.accepted.connect(
-            functools.partial(
-                self.handleGuiEditorAccepted,
-                guiEditor,
-                index,
-                factory,
+            guiEditor.accepted.connect(
+                functools.partial(
+                    self.handleGuiEditorAccepted,
+                    guiEditor,
+                    index,
+                    factory,
+                )
             )
-        )
-        guiEditor.open()
+            guiEditor.open()
 
     def handleGuiEditorAccepted(
         self,
@@ -953,26 +958,27 @@ def handleGuiEditorAccepted(
         index: int,
         factory: ConfigurationFactory,
     ):
-        logger.debug(f'guiEditor accepted with index {index}')
+        with self.guiEditorMutex:
+            logger.debug(f'guiEditor accepted with index {index}')
 
-        modified = editor.inputToFactory(factory)
+            modified = editor.inputToFactory(factory)
 
-        # Still flush to row since remark may be modified
-        self.flushRow(index, factory)
+            # Still flush to row since remark may be modified
+            self.flushRow(index, factory)
 
-        if modified and index == AS_UserActivatedItemIndex():
-            try:
-                if APP().isSystemTrayConnected():
-                    mbox = NewChangesNextTimeMBox()
+            if modified and index == AS_UserActivatedItemIndex():
+                try:
+                    if APP().isSystemTrayConnected():
+                        mbox = NewChangesNextTimeMBox()
 
-                    # Show the MessageBox asynchronously
-                    mbox.open()
-            except Exception:
-                # Any non-exit exceptions
+                        # Show the MessageBox asynchronously
+                        mbox.open()
+                except Exception:
+                    # Any non-exit exceptions
 
-                pass
+                    pass
 
-        editor.accepted.disconnect()
+            editor.accepted.disconnect()
 
     @QtCore.Slot(QtCore.QPoint)
     def handleCustomContextMenuRequested(self, point):
@@ -1073,45 +1079,47 @@ def addServerViaGui(
         windowTitle: str = APPLICATION_NAME,
         **kwargs,
     ):
-        factory = getEmptyFactory(protocol)
+        with self.guiEditorMutex:
+            factory = getEmptyFactory(protocol)
 
-        guiEditor = self.getGuiEditorByFactory(factory, **kwargs)
+            guiEditor = self.getGuiEditorByFactory(factory, **kwargs)
 
-        if guiEditor is None:
-            # Unrecognized. Do nothing
-            return
+            if guiEditor is None:
+                # Unrecognized. Do nothing
+                return
 
-        # Dummy ref
-        setattr(self, '_guiEditorRef1', guiEditor)
+            # Dummy ref
+            setattr(self, '_guiEditorRef1', guiEditor)
 
-        guiEditor.setWindowTitle(windowTitle)
+            guiEditor.setWindowTitle(windowTitle)
 
-        try:
-            guiEditor.factoryToInput(factory)
-        except Exception as ex:
-            # Any non-exit exceptions
+            try:
+                guiEditor.factoryToInput(factory)
+            except Exception as ex:
+                # Any non-exit exceptions
 
-            logger.error(f'error while converting factory to input: {ex}')
+                logger.error(f'error while converting factory to input: {ex}')
 
-        guiEditor.accepted.connect(
-            functools.partial(
-                self.handleAddServerViaGui,
-                guiEditor,
-                factory,
+            guiEditor.accepted.connect(
+                functools.partial(
+                    self.handleAddServerViaGui,
+                    guiEditor,
+                    factory,
+                )
             )
-        )
-        guiEditor.open()
+            guiEditor.open()
 
     def handleAddServerViaGui(
         self,
         editor: GuiEditorWidgetQDialog,
         factory: ConfigurationFactory,
     ):
-        editor.inputToFactory(factory)
+        with self.guiEditorMutex:
+            editor.inputToFactory(factory)
 
-        self.appendNewItemByFactory(factory)
+            self.appendNewItemByFactory(factory)
 
-        editor.accepted.disconnect()
+            editor.accepted.disconnect()
 
     def flushRow(self, row: int, item: ConfigurationFactory):
         for column in list(range(self.columnCount())):