3MFLoader: fixed multiple build items refecering the same object bug (#22663)

* fixed multiple build items refecering the same object bug

* fixed multiple children groups

* clean up

* Update 3MFLoader.js

* Update 3MFLoader.js

Co-authored-by: unknown <[email protected]>
Co-authored-by: Michael Herzog <[email protected]>

examples/jsm/loaders/3MFLoader.js

@@ -1431,7 +1431,7 @@ class ThreeMFLoader extends Loader {
 			for ( let i = 0; i < buildData.length; i ++ ) {
 
 				const buildItem = buildData[ i ];
-				const object3D = objects[ buildItem[ 'objectId' ] ];
+				const object3D = objects[ buildItem[ 'objectId' ] ].clone();
 
 				// apply transform