Visual Composer Problem Narrow Down Data Source

Hello, I have bought your Wildster Theme and enable the “Visual Composer Shortcodes” in the theme options and bought a full visual composer licence and activated it.
Everything seems to work, but if I want to create a “post masonry grid” and try to narrow down the data source in the option panal (for example to show only posts from one category), nothing happens. I click in the field and normally there is something like a auto-fill function. But it shows only the preloader circle and nothing happen. So I can not choose any categorie or tag to narrow down the data source. I also wrote the Visual Composer Support Team. After deactivating your “IshYoBoy Wildster Assets” Plugin, it works to narrow down the data source. But then – of course – the site looks not correct.

So do you have any idea why I can’t choose any category in the optiona panel?

Thanks in advance and Greetings,
Marc