Hello,
Sorry to say but there isn’t any issue with the Product Brands and Product Meta elements to be added under the Custom Single Product layout saving of the Elementor editor. Here is the Video from the Test Site for reference, things working fine there: https://jumpshare.com/v/gijflHVNmI8Fw4EqTGT4
On your Site, the Dashboard > Layouts is showing as Empty: https://snipboard.io/Fgi5Lj.jpg
So, you need to first create a Layout under the Dashboard > Layouts > and in that try using the mentioned Elements. Hopefully, you won’t find any issues by then. Here is the guide to the Layout Builder under the Theme: https://xtemos.com/docs-topic/single-product-page-builder/
Best Regards