diff --git a/src/components/components/CommonComponents.js b/src/components/components/CommonComponents.js
index 9868791fc..0ac8a4319 100644
--- a/src/components/components/CommonComponents.js
+++ b/src/components/components/CommonComponents.js
@@ -12,20 +12,44 @@ import Events from '../../lib/Events';
 import { saveBlob } from '../../lib/utils';
 import GLTFIcon from '../../../assets/gltf.svg';
 
-// @todo Take this out and use updateEntity?
-function changeId(componentName, value) {
-  var entity = AFRAME.INSPECTOR.selectedEntity;
-  if (entity.id !== value) {
-    entity.id = value;
-    Events.emit('entityidchange', entity);
-  }
-}
-
 export default class CommonComponents extends React.Component {
   static propTypes = {
     entity: PropTypes.object
   };
 
+  state = {
+    duplicateId: null,
+    idInputKey: 0
+  };
+
+  changeId = (componentName, value) => {
+    var entity = AFRAME.INSPECTOR.selectedEntity;
+    if (entity.id !== value) {
+      // Ids must be unique; committing a duplicate id breaks entity lookups
+      // done with getElementById or querySelector in components. Refuse the
+      // value, show a message and remount the input so it displays the
+      // entity's current id again.
+      if (value && document.getElementById(value)) {
+        this.setState((state) => ({
+          duplicateId: value,
+          idInputKey: state.idInputKey + 1
+        }));
+        return;
+      }
+      this.setState({ duplicateId: null });
+      entity.id = value;
+      Events.emit('entityidchange', entity);
+    } else {
+      this.setState({ duplicateId: null });
+    }
+  };
+
+  componentDidUpdate(prevProps) {
+    if (prevProps.entity !== this.props.entity && this.state.duplicateId) {
+      this.setState({ duplicateId: null });
+    }
+  }
+
   onEntityUpdate = (detail) => {
     if (detail.entity !== this.props.entity) {
       return;
@@ -125,12 +149,19 @@ export default class CommonComponents extends React.Component {
               ID
             </label>
             <InputWidget
-              onBlur={changeId}
+              key={this.state.idInputKey}
+              onBlur={this.changeId}
               entity={entity}
               name="id"
               value={entity.id}
             />
           </div>
+          {this.state.duplicateId !== null && (
+            <div className="propertyRowError">
+              The id &quot;{this.state.duplicateId}&quot; is already used by
+              another element, the previous id was restored.
+            </div>
+          )}
           <div className="propertyRow">
             <label className="text">class</label>
             <span>{entity.getAttribute('class')}</span>
diff --git a/src/lib/raycaster.js b/src/lib/raycaster.js
index b3ed4a3eb..58b947db2 100644
--- a/src/lib/raycaster.js
+++ b/src/lib/raycaster.js
@@ -73,7 +73,14 @@ export function initRaycaster(inspector) {
     if (event instanceof CustomEvent) {
       return;
     }
-    event.preventDefault();
+    // Don't preventDefault on left click: it would suppress the browser's
+    // default focus transfer, leaving a focused panel input (e.g. the id
+    // field) focused while the selection changes underneath it, so its blur
+    // handler would later commit a stale value to the newly selected entity.
+    if (event.button !== 0) {
+      // Middle click: prevent autoscroll so it can be used for zoom.
+      event.preventDefault();
+    }
     const array = getMousePosition(
       inspector.container,
       event.clientX,
diff --git a/src/style/components.styl b/src/style/components.styl
index 7dd16f42b..867c00422 100644
--- a/src/style/components.styl
+++ b/src/style/components.styl
@@ -137,6 +137,11 @@
   .text
     width 90px
 
+.propertyRowError
+  color var(--color-error)
+  font-size 13px
+  padding 2px 30px 2px 15px
+
 .propertyRowDefined .text
   color var(--color-property-defined)
   font-weight 600
diff --git a/src/style/index.styl b/src/style/index.styl
index 0981cfc55..44a432a46 100644
--- a/src/style/index.styl
+++ b/src/style/index.styl
@@ -12,6 +12,11 @@ body.aframe-inspector-opened
   margin 0
   overflow hidden
 
+  a-scene .a-canvas
+    // mousedown default action is no longer prevented (see raycaster.js), so
+    // block drag-started text selection from anchoring on the canvas
+    user-select none
+
 /* :where(:root) has zero specificity compared to :root, so any user defined :root will override the below rule */
 :where(:root) {
   color-scheme: dark;
@@ -301,9 +306,6 @@ body.aframe-inspector-opened
   .hide
     display none
 
-  .a-canvas.state-dragging
-    cursor grabbing
-
   #rightPanel
     align-items stretch
     display flex
@@ -325,10 +327,6 @@ body.aframe-inspector-opened
   #rightPanel
     pointer-events all
 
-  .aframe-inspector-opened a-scene .a-canvas
-    background-color #191919
-    z-index 9998
-
   .toggle-sidebar
     align-items center
     display flex