bug fix

com.unity.uiwidgets/Runtime/widgets/framework.cs

                         badAncestors.Add(ancestor.widget);
                     }
                     else if (ancestor is RenderObjectElement) {
+                        //temporary work around the version miss match issue between 1.5.4(original) and 1.17.5(changes for local position)
+                        if (this.widget is Positioned) {
+                            break;
+                        }
                         if (this.widget.debugIsValidAncestor(((RenderObjectElement) ancestor).widget)) {
                             break;
                         }

com.unity.uiwidgets/Runtime/gestures/multidrag.cs

             this._pendingDelta = null;
             this._lastPendingEventTimestamp = null;
             this._client.update(details);
-        }
+        } 
 
         public void _up() {
             D.assert(this._arenaEntry != null);
 
 
         public override void dispose() {
-            foreach (var key in this._pointers.Keys) {
+            var keySet = new List<int>(this._pointers.Keys);
+            foreach (var key in keySet) {
                 this._removeState(key);
             }
             D.assert(this._pointers.isEmpty);