fixed serialization when called multiple times

dist/preview release/babylon.max.js

@@ -46424,6 +46424,7 @@ var BABYLON;
         };
         SceneSerializer.Serialize = function (scene) {
             var serializationObject = {};
+            SceneSerializer.ClearCache();
             // Scene
             serializationObject.useDelayedTextureLoading = scene.useDelayedTextureLoading;
             serializationObject.autoClear = scene.autoClear;
@@ -46563,6 +46564,7 @@ var BABYLON;
             if (withParents === void 0) { withParents = false; }
             if (withChildren === void 0) { withChildren = false; }
             var serializationObject = {};
+            SceneSerializer.ClearCache();
             toSerialize = (toSerialize instanceof Array) ? toSerialize : [toSerialize];
             if (withParents || withChildren) {
                 //deliberate for loop! not for each, appended should be processed as well.

src/Tools/babylon.sceneSerializer.ts

@@ -236,6 +236,8 @@
         public static Serialize(scene: Scene): any {
             var serializationObject: any = {};
 
+            SceneSerializer.ClearCache();
+
             // Scene
             serializationObject.useDelayedTextureLoading = scene.useDelayedTextureLoading;
             serializationObject.autoClear = scene.autoClear;
@@ -402,6 +404,8 @@
         public static SerializeMesh(toSerialize: any /* Mesh || Mesh[] */, withParents: boolean = false, withChildren: boolean = false): any {
             var serializationObject: any = {};
 
+            SceneSerializer.ClearCache();
+
             toSerialize = (toSerialize instanceof Array) ? toSerialize : [toSerialize];
 
             if (withParents || withChildren) {