Issue with automatically assigning poster on video elements

1st of all really enjoying all that Grapes has to offer once you've worked through the starting stumbling blocks!

I have a small issue atm regarding videos. I am passing them to the Asset manager with a thumbnail property, which is then applied to the video poster trait when the src is updated. The only problem is this doesn't seem to actually work until the src is changed a couple of times, and then it only applies to the view and not the exported html.

Here's my current code from my plugin...

  defaultType = comps.getType("video");
  comps.addType("video", {
    model: defaultType.model.extend({
      traits: [
        {
          name: 'poster',
          chngeProp: 1,
        },
      ],
    }),
    view: defaultType.view.extend({
      init() {
        this.listenTo(this.model, 'active', this.onActive);
        this.listenTo(this.model, "change:src", this.updatePoster);
      },
      events: {
        dblclick: 'onActive',
      },
      onActive() {
        editor.AssetManager.render(editor.AssetManager.getAll().filter(asset => asset.get('type') == 'video'));
        editor.runCommand("open-assets", {
          target: this.model,
        });
      },
      updatePoster() {
        const src = this.model.get("src");
        const srcOrigin = editor.AssetManager.getAll().filter(asset => asset.get("src") == src);
        let thumb = srcOrigin[0].get("thumb");
        if (thumb != "") {
          let thumbPath = src.substring(0, src.lastIndexOf("/"))+"/"+thumb;
          this.model.getTrait('poster').set("value", thumbPath);
        } else {
          let thumbPath = "";
          this.model.getTrait('poster').set("value", thumbPath);
        }
      },
    }),
  });

and the block simply as

 addName('video') && bm.add('video', {
    label: "Video",
    category: "Extras",
    attributes: {class:'fa fa-youtube-play'},
    content: {
      type: 'video',
      style: {
        "display": "block",
        "min-height": "200px",
        "max-width": "100%",
        "height": "auto",
        "padding": "10px",
      },
      activeOnRender: 1,
    },
  });

I'm guessing I'm just missing a bit of logic in the component model, but not sure what that should be