diff --git a/src/containers/blocks.jsx b/src/containers/blocks.jsx
index c7c9f1e09..c7db7c835 100644
--- a/src/containers/blocks.jsx
+++ b/src/containers/blocks.jsx
@@ -147,6 +147,7 @@ class Blocks extends React.Component {
   }
   componentWillUnmount() {
     this.detachVM()
+    this.onTargetsUpdate.cancel()
     this.workspace.dispose()
     clearTimeout(this.toolboxUpdateTimeout)
   }
diff --git a/src/containers/stage.jsx b/src/containers/stage.jsx
index 44e2fd13f..fd3e03203 100644
--- a/src/containers/stage.jsx
+++ b/src/containers/stage.jsx
@@ -299,22 +299,24 @@ class Stage extends React.Component {
     }
     this.setState({ mouseDownTimeoutId: null })
   }
-  drawDragCanvas(drawableData) {
-    const { data, width, height, x, y } = drawableData
-    this.dragCanvas.width = width
-    this.dragCanvas.height = height
-    // Need to convert uint8array from WebGL readPixels into Uint8ClampedArray
-    // for ImageData constructor. Shares underlying buffer, so it is fast.
-    const imageData = new ImageData(
-      new Uint8ClampedArray(data.buffer),
-      width,
-      height
-    )
+  drawDragCanvas(drawableData, x, y) {
+    const {
+      imageData,
+      x: boundsX,
+      y: boundsY,
+      width: boundsWidth,
+      height: boundsHeight,
+    } = drawableData
+    this.dragCanvas.width = imageData.width
+    this.dragCanvas.height = imageData.height
+    // On high-DPI devices the extracted image is larger than its CSS size
+    this.dragCanvas.style.width = `${boundsWidth}px`
+    this.dragCanvas.style.height = `${boundsHeight}px`
     this.dragCanvas.getContext('2d').putImageData(imageData, 0, 0)
-    // Position so that pick location is at (0, 0) so that  positionDragCanvas()
+    // Position so that pick location is at (0, 0) so that positionDragCanvas()
     // can use translation to move to mouse position smoothly.
-    this.dragCanvas.style.left = `${-x}px`
-    this.dragCanvas.style.top = `${-y}px`
+    this.dragCanvas.style.left = `${boundsX - x}px`
+    this.dragCanvas.style.top = `${boundsY - y}px`
     this.dragCanvas.style.display = 'block'
   }
   clearDragCanvas() {
@@ -334,28 +336,30 @@ class Stage extends React.Component {
     if (drawableId === null) {
       return
     }
-    const drawableData = this.renderer.extractDrawable(drawableId, x, y)
     const targetId = this.props.vm.getTargetIdForDrawableId(drawableId)
     if (targetId === null) {
       return
     }
+    const target = this.props.vm.runtime.getTargetById(targetId)
 
     // Only start drags on non-draggable targets in editor drag mode
-    if (!this.props.useEditorDragStyle) {
-      const target = this.props.vm.runtime.getTargetById(targetId)
-      if (!target.draggable) {
-        return
-      }
+    if (!(this.props.useEditorDragStyle || target.draggable)) {
+      return
     }
 
+    const [scratchMouseX, scratchMouseY] = this.getScratchCoords(x, y)
+    const offsetX = target.x - scratchMouseX
+    const offsetY = -(target.y + scratchMouseY)
+
     this.props.vm.startDrag(targetId)
     this.setState({
       isDragging: true,
       dragId: targetId,
-      dragOffset: drawableData.scratchOffset,
+      dragOffset: [offsetX, offsetY],
     })
     if (this.props.useEditorDragStyle) {
-      this.drawDragCanvas(drawableData)
+      const drawableData = this.renderer.extractDrawableScreenSpace(drawableId)
+      this.drawDragCanvas(drawableData, x, y)
       this.positionDragCanvas(x, y)
       this.props.vm.postSpriteInfo({ visible: false })
     }
diff --git a/src/lib/project-save-hoc.jsx b/src/lib/project-save-hoc.jsx
index f2d02a968..17d95948d 100644
--- a/src/lib/project-save-hoc.jsx
+++ b/src/lib/project-save-hoc.jsx
@@ -1,4 +1,5 @@
 import { connect } from 'react-redux'
+import { withRouter } from 'react-router-dom'
 import React from 'react'
 import PropTypes from 'prop-types'
 import {
@@ -225,14 +226,16 @@ const ProjectSaveHOC = (WrappedComponent) => {
     dispatch: PropTypes.func,
   }
 
-  return connect((state) => ({
+  const mapStateToProps = (state, ownProps) => ({
     isEduGame: state.scratchGui.eduLayer.enabled,
     projectId: state.scratchGui.project.id,
     projectName: state.scratchGui.project.name,
-    routeProject: (state.router.params || {}).projectId || null,
+    routeProject: ownProps.match.params.projectId || null,
     userId: state.scratchGui.project.userId,
     vm: state.scratchGui.vm,
-  }))(ProjectSaveComponent)
+  })
+
+  return withRouter(connect(mapStateToProps)(ProjectSaveComponent))
 }
 
 export default ProjectSaveHOC
diff --git a/src/lib/unsaved-project-blocker.jsx b/src/lib/unsaved-project-blocker.jsx
index 81c82a903..b1e27d044 100644
--- a/src/lib/unsaved-project-blocker.jsx
+++ b/src/lib/unsaved-project-blocker.jsx
@@ -3,44 +3,56 @@ import { connect } from 'react-redux'
 import PropTypes from 'prop-types'
 import { history } from './app-state-hoc.jsx'
 
+const LEAVE_MESSAGE =
+  'Möchtest du die Seite wirklich verlassen? Dein Projekt geht ohne Speichern verloren!'
+
 const UnsavedProjectBlockerHOC = (WrappedComponent) => {
   class UnsavedProjectBlocker extends React.Component {
+    constructor(props) {
+      super(props)
+      this.unblockRouter = null
+    }
     stopBrowserNavigation(event) {
       event.preventDefault()
       event.returnValue = ''
     }
-    routerBlock() {
-      const unblock = history.block(() => {
-        return window.confirm(
-          'Möchtest du die Seite wirklich verlassen? Dein Projekt geht ohne Speichern verloren!'
-        )
-      })
-
-      return () => {
-        unblock()
+    block() {
+      if (this.unblockRouter) {
+        return
+      }
+      window.addEventListener('beforeunload', this.stopBrowserNavigation)
+      // history v4 shows a string prompt via window.confirm
+      this.unblockRouter = history.block(LEAVE_MESSAGE)
+    }
+    unblock() {
+      window.removeEventListener('beforeunload', this.stopBrowserNavigation)
+      if (this.unblockRouter) {
+        this.unblockRouter()
+        this.unblockRouter = null
       }
     }
+    syncBlocker() {
+      if (process.env.NODE_ENV !== 'production' || typeof window !== 'object') {
+        return
+      }
+      if (this.props.isProjectUnsaved) {
+        this.block()
+      } else {
+        this.unblock()
+      }
+    }
+    componentDidMount() {
+      this.syncBlocker()
+    }
     componentDidUpdate(oldProps) {
       if (this.props.isProjectUnsaved !== oldProps.isProjectUnsaved) {
-        if (
-          process.env.NODE_ENV === 'production' &&
-          typeof window === 'object'
-        ) {
-          if (this.props.isProjectUnsaved) {
-            // Warn before navigating away
-            window.addEventListener('beforeunload', this.stopBrowserNavigation)
-            this.routerBlock()
-          } else {
-            window.removeEventListener(
-              'beforeunload',
-              this.stopBrowserNavigation
-            )
-          }
-        }
+        this.syncBlocker()
       }
     }
     componentWillUnmount() {
-      window.removeEventListener('beforeunload', this.stopBrowserNavigation)
+      if (typeof window === 'object') {
+        this.unblock()
+      }
     }
     render() {
       const {