diff --git a/toonz/sources/toonz/comboviewerpane.cpp b/toonz/sources/toonz/comboviewerpane.cpp
index cbf7282..f85084e 100644
--- a/toonz/sources/toonz/comboviewerpane.cpp
+++ b/toonz/sources/toonz/comboviewerpane.cpp
@@ -381,7 +381,8 @@ void ComboViewerPanel::showEvent(QShowEvent *event) {
   // onXshLevelSwitched(TXshLevel*)： changeWindowTitle() + updateFrameRange()
   ret = ret && connect(levelHandle, SIGNAL(xshLevelSwitched(TXshLevel *)), this,
                        SLOT(onXshLevelSwitched(TXshLevel *)));
-
+  ret = ret && connect(levelHandle, SIGNAL(xshLevelTitleChanged()), this,
+                       SLOT(changeWindowTitle()));
   // updateFrameRange(): update the frame slider's range
   ret = ret && connect(levelHandle, SIGNAL(xshLevelChanged()), this,
                        SLOT(updateFrameRange()));
@@ -410,13 +411,38 @@ void ComboViewerPanel::showEvent(QShowEvent *event) {
 
 void ComboViewerPanel::hideEvent(QHideEvent *event) {
   StyleShortcutSwitchablePanel::hideEvent(event);
-  TApp *app = TApp::instance();
-  disconnect(app->getCurrentScene());
-  disconnect(app->getCurrentLevel());
-  disconnect(app->getCurrentFrame());
-  disconnect(app->getCurrentObject());
-  disconnect(app->getCurrentXsheet());
-  disconnect(app->getCurrentTool());
+  TApp *app                    = TApp::instance();
+  TFrameHandle *frameHandle    = app->getCurrentFrame();
+  TSceneHandle *sceneHandle    = app->getCurrentScene();
+  TXshLevelHandle *levelHandle = app->getCurrentLevel();
+  TObjectHandle *objectHandle  = app->getCurrentObject();
+  TXsheetHandle *xshHandle     = app->getCurrentXsheet();
+
+  disconnect(xshHandle, SIGNAL(xsheetChanged()), this, SLOT(onSceneChanged()));
+
+  disconnect(sceneHandle, SIGNAL(sceneChanged()), this, SLOT(onSceneChanged()));
+  disconnect(sceneHandle, SIGNAL(nameSceneChanged()), this,
+             SLOT(changeWindowTitle()));
+  disconnect(sceneHandle, SIGNAL(sceneSwitched()), this,
+             SLOT(onSceneChanged()));
+  disconnect(levelHandle, SIGNAL(xshLevelSwitched(TXshLevel *)), this,
+             SLOT(onXshLevelSwitched(TXshLevel *)));
+  disconnect(levelHandle, SIGNAL(xshLevelChanged()), this,
+             SLOT(changeWindowTitle()));
+  disconnect(levelHandle, SIGNAL(xshLevelTitleChanged()), this,
+             SLOT(changeWindowTitle()));
+  disconnect(levelHandle, SIGNAL(xshLevelChanged()), this,
+             SLOT(updateFrameRange()));
+
+  disconnect(frameHandle, SIGNAL(frameSwitched()), this,
+             SLOT(changeWindowTitle()));
+  disconnect(frameHandle, SIGNAL(frameSwitched()), this,
+             SLOT(onFrameChanged()));
+  disconnect(frameHandle, SIGNAL(frameTypeChanged()), this,
+             SLOT(onFrameTypeChanged()));
+
+  disconnect(app->getCurrentTool(), SIGNAL(toolSwitched()), m_sceneViewer,
+             SLOT(onToolSwitched()));
 
   m_flipConsole->setActive(false);
 }
diff --git a/toonz/sources/toonz/viewerpane.cpp b/toonz/sources/toonz/viewerpane.cpp
index f2b3f5a..55d882a 100644
--- a/toonz/sources/toonz/viewerpane.cpp
+++ b/toonz/sources/toonz/viewerpane.cpp
@@ -241,9 +241,11 @@ void SceneViewerPanel::showEvent(QShowEvent *event) {
 
   ret = ret && connect(xshHandle, SIGNAL(xsheetChanged()), this,
                        SLOT(onSceneChanged()));
-
+  ret = ret && connect(sceneHandle, SIGNAL(sceneSwitched()), this,
+                       SLOT(onSceneChanged()));
   ret = ret && connect(sceneHandle, SIGNAL(sceneChanged()), this,
                        SLOT(onSceneChanged()));
+
   ret = ret && connect(sceneHandle, SIGNAL(nameSceneChanged()), this,
                        SLOT(changeWindowTitle()));
 
@@ -289,7 +291,8 @@ void SceneViewerPanel::hideEvent(QHideEvent *event) {
   disconnect(sceneHandle, SIGNAL(sceneChanged()), this, SLOT(onSceneChanged()));
   disconnect(sceneHandle, SIGNAL(nameSceneChanged()), this,
              SLOT(changeWindowTitle()));
-
+  disconnect(sceneHandle, SIGNAL(sceneSwitched()), this,
+             SLOT(onSceneChanged()));
   disconnect(levelHandle, SIGNAL(xshLevelSwitched(TXshLevel *)), this,
              SLOT(onXshLevelSwitched(TXshLevel *)));
   disconnect(levelHandle, SIGNAL(xshLevelChanged()), this,
@@ -665,6 +668,16 @@ void SceneViewerPanel::onFrameTypeChanged() {
 
 //-----------------------------------------------------------------------------
 
+bool SceneViewerPanel::isFrameAlreadyCached(int frame) {
+  if (m_sceneViewer->isPreviewEnabled()) {
+    class Previewer *pr = Previewer::instance();
+    return pr->isFrameReady(frame - 1);
+  } else
+    return true;
+}
+
+//-----------------------------------------------------------------------------
+
 void SceneViewerPanel::onPreferenceChanged(const QString &prefName) {
   m_flipConsole->onPreferenceChanged(prefName);
   StyleShortcutSwitchablePanel::onPreferenceChanged(prefName);
diff --git a/toonz/sources/toonz/viewerpane.h b/toonz/sources/toonz/viewerpane.h
index 327c130..62c8af2 100644
--- a/toonz/sources/toonz/viewerpane.h
+++ b/toonz/sources/toonz/viewerpane.h
@@ -60,6 +60,8 @@ public:
   bool widgetInThisPanelIsFocused() override {
     return m_sceneViewer->hasFocus();
   }
+  // reimplementation of FlipConsoleOwner::isFrameAlreadyCached
+  bool isFrameAlreadyCached(int frame) override;
 
 protected:
   void showEvent(QShowEvent *) override;