diff --git a/applets/taskmanager/package/contents/ui/GroupDialog.qml b/applets/taskmanager/package/contents/ui/GroupDialog.qml
--- a/applets/taskmanager/package/contents/ui/GroupDialog.qml
+++ b/applets/taskmanager/package/contents/ui/GroupDialog.qml
@@ -125,6 +125,12 @@
                     }
                 }
 
+                onAnimatingChanged: {
+                    if (!animating) {
+                        updateSize();
+                    }
+                }
+
                 Repeater {
                     id: groupRepeater
 
@@ -140,7 +146,13 @@
                         return -1;
                     }
 
-                    onCountChanged: updateSize();
+                    onItemAdded: updateSize()
+
+                    onItemRemoved: {
+                        if (groupDialog.visible && index > 0 && index == count) {
+                            updateSize();
+                        }
+                    }
                 }
             }
         }
@@ -246,7 +258,7 @@
         // Setting VisualDataModel.rootIndex drops groupRepeater.count to 0
         // before the actual row count. updateSize is therefore invoked twice;
         // only update size once the repeater count matches the model role.
-        } else if (visualParent.childCount == groupRepeater.count) {
+        } else if (!groupRepeater.aboutToPopulate || visualParent.childCount == groupRepeater.count) {
             var task;
             var maxWidth = 0;
             var maxHeight = 0;
diff --git a/applets/taskmanager/package/contents/ui/Task.qml b/applets/taskmanager/package/contents/ui/Task.qml
--- a/applets/taskmanager/package/contents/ui/Task.qml
+++ b/applets/taskmanager/package/contents/ui/Task.qml
@@ -68,6 +68,12 @@
     }
 
     onChildCountChanged: {
+        if (!childCount && groupDialog.visualParent == task) {
+            groupDialog.visible = false;
+
+            return;
+        }
+
         if (containsMouse) {
             groupDialog.activeTask = null;
         }