diff --git a/Engine/EffectInstance.cpp b/Engine/EffectInstance.cpp
index 17e0281f64..1e1176a88d 100644
--- a/Engine/EffectInstance.cpp
+++ b/Engine/EffectInstance.cpp
@@ -2217,7 +2217,12 @@ EffectInstance::Implementation::tiledRenderingFunctor(const RectToRender & rectT
 #endif
     EffectTLSDataPtr tls = tlsData->getOrCreateTLSData();
 
-    assert( !rectToRender.rect.isNull() );
+    if ( rectToRender.rect.isNull() ) {
+        // should never happen, but crashes when loading
+        // https://github.com/NatronGitHub/Natron/files/4630686/maskissue.log
+        //assert(false);
+        return eRenderingFunctorRetOK;
+    }
 
     /*
      * renderMappedRectToRender is in the mapped mipmap level, i.e the expected mipmap level of the render action of the plug-in
diff --git a/Gui/NodeGraph.cpp b/Gui/NodeGraph.cpp
index a4054b8535..6a682e0353 100644
--- a/Gui/NodeGraph.cpp
+++ b/Gui/NodeGraph.cpp
@@ -176,7 +176,6 @@ NodeGraph::NodeGraph(Gui* gui,
     _imp->_bR->setPos( _imp->_bR->mapFromScene( QPointF(NATRON_SCENE_MAX, NATRON_SCENE_MIN) ) );
     _imp->_bL->setPos( _imp->_bL->mapFromScene( QPointF(NATRON_SCENE_MIN, NATRON_SCENE_MIN) ) );
     centerOn(0, 0);
-    setSceneRect(NATRON_SCENE_MIN, NATRON_SCENE_MIN, NATRON_SCENE_MAX, NATRON_SCENE_MAX);
 
     setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
     setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
diff --git a/Gui/NodeGraph30.cpp b/Gui/NodeGraph30.cpp
index 21d6ccd90a..a4be3141be 100644
--- a/Gui/NodeGraph30.cpp
+++ b/Gui/NodeGraph30.cpp
@@ -179,7 +179,6 @@ NodeGraph::wheelEventInternal(bool ctrlDown,
         _imp->_accumDelta += delta;
         if (std::abs(_imp->_accumDelta) > 60) {
             scaleFactor = pow( NATRON_WHEEL_ZOOM_PER_DELTA, _imp->_accumDelta );
-            // setSceneRect(NATRON_SCENE_MIN,NATRON_SCENE_MIN,NATRON_SCENE_MAX,NATRON_SCENE_MAX);
             scale(scaleFactor, scaleFactor);
             _imp->_accumDelta = 0;
         }
diff --git a/Gui/NodeGraph35.cpp b/Gui/NodeGraph35.cpp
index 9ee8f7b521..5cdacc6c4e 100644
--- a/Gui/NodeGraph35.cpp
+++ b/Gui/NodeGraph35.cpp
@@ -484,14 +484,17 @@ NodeGraph::showMenu(const QPoint & pos)
     if (ret == findAction) {
         popFindDialog();
     } else if (ret == duplicateAction) {
-        QRectF rect = visibleSceneRect();
-        duplicateSelectedNodes( rect.center() );
+        // Duplicate at mouse click position:
+        QPointF scenePos = mapToScene( mapFromGlobal(pos) );
+        cloneSelectedNodes(scenePos);
     } else if (ret == cloneAction) {
-        QRectF rect = visibleSceneRect();
-        cloneSelectedNodes( rect.center() );
+        // Clone at mouse click position:
+        QPointF scenePos = mapToScene( mapFromGlobal(pos) );
+        cloneSelectedNodes(scenePos);
     } else if (ret == pasteAction) {
-        QRectF rect = visibleSceneRect();
-        pasteNodeClipBoards( rect.center() );
+        // Paste at mouse click position:
+        QPointF scenePos = mapToScene( mapFromGlobal(pos) );
+        cloneSelectedNodes(scenePos);
     }
 } // NodeGraph::showMenu
 
diff --git a/Gui/NodeGraph40.cpp b/Gui/NodeGraph40.cpp
index 475d85277e..f0b73ce8ca 100644
--- a/Gui/NodeGraph40.cpp
+++ b/Gui/NodeGraph40.cpp
@@ -189,7 +189,7 @@ NodeGraph::pasteNodeClipBoards(const QPointF& pos)
         return false;
     }
 
-    _imp->pasteNodesInternal(cb, pos, true, &newNodes);
+    _imp->pasteNodesInternal(cb, _imp->_root->mapFromScene(pos), true, &newNodes);
 
     return true;
 }
@@ -197,7 +197,7 @@ NodeGraph::pasteNodeClipBoards(const QPointF& pos)
 bool
 NodeGraph::pasteNodeClipBoards()
 {
-    QPointF position = _imp->_root->mapFromScene( mapToScene( mapFromGlobal( QCursor::pos() ) ) );
+    QPointF position = mapToScene( mapFromGlobal( QCursor::pos() ) );
 
     return pasteNodeClipBoards(position);
 }
@@ -215,13 +215,13 @@ NodeGraph::duplicateSelectedNodes(const QPointF& pos)
     NodeClipBoard tmpClipboard;
     _imp->copyNodesInternal(_imp->_selection, tmpClipboard);
     std::list<std::pair<std::string, NodeGuiPtr> > newNodes;
-    _imp->pasteNodesInternal(tmpClipboard, pos, true, &newNodes);
+    _imp->pasteNodesInternal(tmpClipboard, _imp->_root->mapFromScene(pos), true, &newNodes);
 }
 
 void
 NodeGraph::duplicateSelectedNodes()
 {
-    QPointF scenePos = _imp->_root->mapFromScene( mapToScene( mapFromGlobal( QCursor::pos() ) ) );
+    QPointF scenePos = mapToScene( mapFromGlobal( QCursor::pos() ) );
 
     duplicateSelectedNodes(scenePos);
 }
@@ -337,7 +337,7 @@ NodeGraph::cloneSelectedNodes(const QPointF& scenePos)
 void
 NodeGraph::cloneSelectedNodes()
 {
-    QPointF scenePos = _imp->_root->mapFromScene( mapToScene( mapFromGlobal( QCursor::pos() ) ) );
+    QPointF scenePos = mapToScene( mapFromGlobal( QCursor::pos() ) );
 
     cloneSelectedNodes(scenePos);
 } // cloneSelectedNodes
@@ -457,7 +457,10 @@ NodeGraph::centerOnAllNodes()
             }
         }
     }
-    QRectF bbox( xmin, ymin, (xmax - xmin), (ymax - ymin) );
+    // Move the scene so that topleft of the viewing area is at 0,0, and avoid issues
+    // when topleft has negative coords.
+    moveRootInternal(-xmin, -ymin);
+    QRectF bbox( 0, 0, (xmax - xmin), (ymax - ymin) );
     fitInView(bbox, Qt::KeepAspectRatio);
 
     double currentZoomFactor = transform().mapRect( QRectF(0, 0, 1, 1) ).width();
diff --git a/Gui/NodeGraphUndoRedo.cpp b/Gui/NodeGraphUndoRedo.cpp
index 6c4f6b2bb4..9379d27db5 100644
--- a/Gui/NodeGraphUndoRedo.cpp
+++ b/Gui/NodeGraphUndoRedo.cpp
@@ -166,6 +166,7 @@ AddMultipleNodesCommand::undo()
     for (std::list<ViewerInstance* >::iterator it = viewersToRefresh.begin(); it != viewersToRefresh.end(); ++it) {
         (*it)->renderCurrentFrame(true);
     }
+    _graph->updateNavigator();
 }
 
 void
@@ -212,6 +213,7 @@ AddMultipleNodesCommand::redo()
     }
 
     _firstRedoCalled = true;
+    _graph->updateNavigator();
 }
 
 RemoveMultipleNodesCommand::RemoveMultipleNodesCommand(NodeGraph* graph,
@@ -246,6 +248,7 @@ RemoveMultipleNodesCommand::RemoveMultipleNodesCommand(NodeGraph* graph,
         }
         _nodes.push_back(n);
     }
+    setText( tr("Remove node(s)") );
 }
 
 RemoveMultipleNodesCommand::~RemoveMultipleNodesCommand()
@@ -258,7 +261,6 @@ RemoveMultipleNodesCommand::~RemoveMultipleNodesCommand()
             }
         }
     }
-    setText( tr("Remove node(s)") );
 }
 
 void
@@ -310,6 +312,7 @@ RemoveMultipleNodesCommand::undo()
 
     _isRedone = false;
     _graph->scene()->update();
+    _graph->updateNavigator();
 } // RemoveMultipleNodesCommand::undo
 
 void
@@ -402,6 +405,7 @@ RemoveMultipleNodesCommand::redo()
     _graph->updateNavigator();
 
     _graph->scene()->update();
+    _graph->updateNavigator();
 } // redo
 
 ConnectCommand::ConnectCommand(NodeGraph* graph,